COVENANT UNIVERSITYcovenantuniversity.edu.ng/content/download/49927/339128/version/2... · 1. With...
-
Upload
nguyenhanh -
Category
Documents
-
view
219 -
download
0
Transcript of COVENANT UNIVERSITYcovenantuniversity.edu.ng/content/download/49927/339128/version/2... · 1. With...
COVENANT UNIVERSITY
ALPHA SEMESTER TUTORIAL KIT (VOL. 2)
P R O G R A M M E : C H E M I S T R Y
400 LEVEL
1
DISCLAIMER
The contents of this document are intended for practice and learning purposes at the undergraduate
level. The materials are from different sources including the internet and the contributors do not
in any way claim authorship or ownership of them. The materials are also not to be used for any
commercial purpose.
2
LIST OF COURSES
CHM411: Quality Control
CHM414: Fertilizer and Agrochemicals
CHM416: Detergent and Cosmetic Chemistry
CHM418: Natural Products
CHM431: Polymer Chemistry
CHM432: Mineral Processing
CHM439: Analysis of Selected Materials
*Not included
3
COURSE CODE: CHM 411 COURSE TITLE: QUALITY CONTROL Section 1
1. With the aid of a diagram, briefly explain the following terms AQL, LTPD, β and α.
2. List 4 points each on application of SPC to airline and grocery store services.
3. Explain three (3) quality control standards that occur in a textile company.
4. The Noise King Muffler Shop, a high-volume installer of replacement exhaust muffler
systems, just received a shipment of 1,000 mufflers. The sampling plan for inspecting
these mufflers calls for a sample size n = 60 and an acceptance number c = 1. The contract
with the muffler manufacturer calls for an AQL of 1 defective muffler per 100 and an LTPD
of 6 defective mufflers per 100.
(i) Determine the producer’s risk and the consumer’s risk for the plan and comment on it.
5. The local newspaper receives several complaints per day about typographic errors. Over
a seven-day period, the publisher has received calls from readers reporting the following
number of errors: 4,3, 2, 6, 7, 3, and 9.
(i) What type of control chart(s) should be used by the publisher?
(ii) Develop a control chart using the data above and comment on it.
6. Write short notes on the following:
(i) The goal of acceptance sampling. (ii) Control charts. (iii) Range chart.
7. A quality control inspector at the Cocoa Fizz soft drink company has taken ten samples
with four observations each of the volume of bottles filled. From Table1.1 below, compute
the average range and the average mean of the bottling operation. Use the results to develop
three-sigma control limits for the bottling operation.
Table1.1
Sample No
1 2 3 4 5 6 7 8 9 10
Observations
Sample(bottle volume in cl)
1 15.85 16.12 16.00 16.20 15.74 15.94 15.75 15.82 16.04 15.64
2 16.02 16.00 15.91 15.85 15.86 16.01 16.21 15.94 15.98 15.86
3 15.83 15.85 15.94 15.74 16.21 16.14 16.01 16.02 15.83 15.94
A2 - 1.88 1.02 0.73 0.58 0.48 0.42 0.37 0.34 0.31
4
TUTORIAL ANSWERS
QUESTION 1
Figure1: An OC curve showing producer’s risk and consumer’s risk Acceptable Quality Level (AQL): AQL is a small percentage of defects that consumers are
willing to accept. It is generally in the order of 1–2 percent.
Lot Tolerance Percent Defective (LTPD): The LTPD is the upper limit of the percentage of
defective items consumers are willing to tolerate.
Consumer’s Risk (β): This is the chance of accepting a lot that contains a greater number of
defects than the LTPD limit. This is the probability of making a Type II error—that is, accepting
a lot that is truly “bad.” Consumer’s risk is generally denoted by beta (β).
Producer’s risk (α): This is the chance that a lot containing an acceptable quality level will be
rejected. This is the probability of making a Type I error—that is, rejecting a lot that is “good.” It
is generally denoted by alpha (α).
QUESTION 2
Applying Statistical Process Control to Services
Airlines
Flight delays, lost luggage and luggage handling, waiting time at ticket counters/check-in, agent
and flight attendant courtesy
Grocery stores
Waiting time for service, customer complaints, cleanliness & quality of food items
5
QUESTION 3
(i) Flame Resistance: This is the ability of fabric to resist burning. The extent of flame resistance
is dictated by the intended end use for the fabric. The application must pass vertical flame test as
well as tunnel test.
(ii) Crocking Resistance: This is fabric's colourfastness. To measure for colourfastness to
crocking, the fabric to be tested is rubbed with squares of white cotton fabric (wet and dry) under
controlled pressure for a specified number of times. The amount of colour transferred to the white
test squares is matched to a control chart and a rating is established as follows:
Class 5 = no color transfer Class 1 = high degree of color transfer
(iii)Ultra Violet Light Resistance This is fabric's resistance to fading. To measure for
colourfastness to light, the fabric to be tested is exposed under specific conditions to a controlled
light source which simulates the sun's rays. At timed intervals, the test swatch is compared to a
gray scale and the degree of fading is rated as follows: Class 5 = no fading Class 1 = high degree
of fading
QUESTION 4
Let p = 0.01.
Multiplying n by p, 60(0.01) = 0.60. Locate 0.60 in Table 1.0. Under the column for c = 1. The probability of acceptance (Pa): 0.878.
Repeat this process for a range of p values.
(a) F.1 Table 1.0: Values for the operating characteristic curve with n = 60 AND c= 1
PROPORTION PROBABILITY OF c OR LESS DEFECTIVE DEFECTS
(p) np (Pa)
0.01 (AQL) 0.6 0.878 0.02 1.2 0.663 0.03 1.8 0.463 0.04 2.4 0.308 0.05 3.0 0.199 0.06 (LTPD) 3.6 0.126 0.07 4.2 0.078 0.08 4.8 0.048 0.09 5.4 0.029 0.10 6.0 0.017
(b) ( When p = AQL, the producer’s risk, α, is 1 minus the probability of acceptance.
α= 1.000 - 0.878 = 0.122 When p = LTPD, the consumer’s risk, β, equals the probability of acceptance.
β = 0.126
6
Comment: The plan provides a producer’s risk of 12.2 percent and a consumer’s risk of 12.6
percent. Both values are higher than the values usually acceptable for plans of this type (5 and 10
percent, respectively). The risks can be adjusted by changing the sample size.
QUESTION 5
(i) The publisher should use a C-chart.
Days 1 2 3 4 5 6 7 Total
Number of Complaints 4 3 2 6 7 4 9 35
The average daily number of complaints is 35 / 7 5.0
5.0 3 5 11.708
5.0 3 5 1.708 0
UCL c z c
LCL c z c
Control Chart C
Comment: Variation is in control. Hence the process is in control, since all the points fall between the control limits.
4
3
2
6
7
4
9
00.5
11.5
22.5
33.5
44.5
55.5
66.5
77.5
88.5
99.510
10.511
11.512
12.513
1 2 3 4 5 6 7
No
of
Co
mp
lain
ts
Days
Control Chart CUCL
CL
LCL
7
QUESTION 6
(i)The goal of acceptance sampling is to determine criteria for acceptance or rejection based on
lot size, sample size, and the desired level of confidence.
(ii) A control chart also called process chart are used to determine whether a process should be
continued or should be adjusted to achieve the desired quality. They are used to monitor the extent
of variability in the quality standard of the finished items from a predetermined standard. A
process control chart has a central line, an upper control limit and a lower control limit as shown
below. if the process is in control, nearly all points will lie within the upper control limit (UCL)
and the lower control limit (LCL). A process is out of control when a plot of data reveals that one or
more samples fall outside the control limits.
(iii) The Range chart: This is a control chart used to monitor changes in the dispersion or
variability of process. A range is normally defined as the difference between the largest and the
smallest values in a sample. The R-chart is useful in monitoring product quality ranges so as to
ensure that the variability is kept within acceptable limits. The center line of the control chart is
the average range, and the upper and lower control limits are computed as follows:
4
3
CL R
UCL D R
LCL D R
8
QUESTION 7
Table1.1
Sample No
1 2 3 4 5 6 7 8 9 10
Observations
Sample(bottle volume in cl)
1 15.85 16.12 16.00 16.20 15.74 15.94 15.75 15.82 16.04 15.64
2 16.02 16.00 15.91 15.85 15.86 16.01 16.21 15.94 15.98 15.86
3 15.83 15.85 15.94 15.74 16.21 16.14 16.01 16.02 15.83 15.94 Total
Average mean 15.90 15.99 15.95 15.93 15.94 16.03 15.99 15.93 15.95 15.81 15.94 Average Range 0.19 0.27 0.09 0.46 0.47 0.2 0.46 0.2 0.21 0.3 0.29
Upper control limit (UCL) =
Lower control limit (LCL) =
where = average of the sample means = average range of the samples = factor obtained from Table 1.1
Notice that is a factor that includes three standard deviations of ranges and is dependent on the
sample size being considered The value of is obtained from a Table. For n = 3, = 1.02
This leads to the following limits: The center of the control chart = CL=15.94cl
Factors for three-sigma control limits of and R-charts Factors for chart Factors for R- Chart
Sample Size n A2 D3 D4
2 1.88 0 3.27
3 1.02 0 2.57
4 0.73 0 2.28
5 0.58 0 2.11
6 0.48 0 2.00
7 0.42 0.08 1.92
8 0.37 0.14 1.86
9 0.34 0.18 1.82
10 0.31 0.22 1.78
11 0.29 0.26 1.74
OPERATING CHARACTERISTIC CURVE TABLE F.1
2X A R2X A R
X
R
2A
2A
2A2A
2
2
15.94 1.02 .29 16.24
15.94 1.02 .29 15.64
UCL x A R
LCL x A R
X
X
9
Table 1: Cumulative Poisson Probabilities
X np0 1 2 3 4 5 6 7 8 9 10 11 12 13 .50 .607 .910 .986 .998 1.000 .55 .577 .894 .982 .998 1.000 .60 .549 .878 .977 .997 1.000 .65 .522 .861 .972 .996 .999 1.000 .70 .497 .844 .966 .994 .999 1.000 .75 .472 .827 .959 .993 .999 1.000 .80 .449 .809 .991 .999 1.000 1.0 .368 .736 .920 .981 .996 .999 1.000 1.1 .333 .699 .900 .974 .995 .999 1.000 1.2 .301 .663 .879 .966 .992 .998 1.000 1.3 .273 .627 .857 .989 .998 1.000 1.7 .183 .493 .757 .907 .970 .992 .998 1.000 1.8 .165 .463 .731 .891 .964 .990 .997 .999 1.000 1.9 .150 .434 .704 .875 .987 .997 .999 1.000 2.0 .135 .406 .677 .857 .947 .983 .995 .999 1.000 2.2 .111 .355 .623 .819 .928 .975 .993 .998 1.000 2.4 .091.308 .570 .779 .904 .964 .988 .997 .999 1.000 2.6 .074 .267 .518 .736 .877 .983 .995 .999 1.000 2.8 .061 .231 .469 .692 .848 .935 .976 .992 .998 .999 1.000 3.0 .050 .199 .423 .647 .815 .916 .966 .988 .996 .999 1.000 3.2 .041 .171 .380 .603 .781 .895 .983 .994 .998 1.000 3.4 .033 .147 .340 .558 .744 .871 .942 .977 .992 .997 .999 1.000 3.6 .027 .126 .303 .515 .706 .844 .927 .969 .988 .996 .999 1.000 3.8 .022 .107 .269 .473 .668 .816 .909 .984 .994 .998 .999 1.000 4.2 .015 .078 .210 .395 .590 .753 .867 .936 .972 .989 .996 .999 1.000 4.4 .012 .066 .185 .359 .551 .720 .844 .921 .964 .985 .994 .998 .999 1.000 4.6 .010 .056 .163 .326 .513 .686 .818 .905 .980 .992 .997 .999 1.000 4.8 .008 .048 .143 .294 .476 .651 .791 .887 .944 .975 .990 .996 .999 1.000 5.0 .007 .040 .125 .265 .440 .616 .762 .867 .932 .968 .986 .995 .998 .999 5.2 .006 .034 .109 .238 .406 .581 .732 .845 .918 .960 .982 .993 .997 .999 5.4 .005 .029 .213 .373 .546 .702 .822 .903 .977 .990 .996 .999 5.6 .004 .024 .082 .191 .342 .512 .670 .797 .886 .941 .972 .988 .995 .998 6.0 .002 .017 .062 .151 .285 .446 .606 .744 .847 .916 .980 .991 .996 6.2 .002 .015 .054 .134 .259 .414 .574 .716 .826 .902 .949 .975 .989 .995
10
Section 2
Tutorial Questions for CHM 411
1. (a) What are the most important factors to be considered in brewing quality beer outside
recipe formulation?
(b) Enumerate the basic reactions of glycolysis leading to the formation of diacetyl in the
brewing process.
2. (a) Discuss the three major aspects of quality control in brewing.
(b) Vividly describe the role and significance of a pharmacopoeia to the pharmaceutical
industry.
3. (a) Outline the modules operandi of Good Manufacturing Practice.
(b) List the items for self-inspection during the validation process.
SOLUTION
1. (a) Yeast Strain Selection:
Once the recipe has been chosen, the next task that will have the biggest impact on the final beer
is yeast strain choice. Brewers have a wide selection of strains to choose from. The strain should
be chosen based on the style of beer, the fermentation temperature, original gravity, and time
available for conditioning.
Pitch Rate:
Beers typically have a reduced ester profile and are characterized as clean with discernable malt
character. It is very important to recognize that pitch rate is directly related to ester production.
Increasing the quantity of yeast pitched is the most effective method of reducing the ester profile
in the finished beer. A minimum of 12 million cells per milliliter is recommended to keep esters
at a minimum.
Fermentation Temperature:
The best results will be achieved by pitching at least 12 million cells per milliliter into cold and
well aerated wort (48 to 58°F, 9 to 15°C). If a faster primary fermentation is desired or one is
11
pitching less yeast, then it is best to start a little bit warmer and then cool to the desired fermentation
temperature once signs of fermentation are evident.
(b)
2. (a) There are three major points to controlling quality: Equipment, Wort, and Yeast Management
Equipment:
It is essential to know your system and its limitations. Many brew systems have weak points that can
potentially cause problems. Dead ends and shadow areas that do not receive adequate recirculation of
chemical must be avoided if possible or must be manually cleaned and inspected. A consistent cleaning
and sanitizing regimen must be followed. Documentation of the cleaning process and chemical usage
rates are essential for consistency and to avoid confusion that could lead to inadequate cleaning.
Wort:
If you are confident in your equipment, it is time to focus on your wort. If your equipment is clean and
well maintained, it is relatively easy to produce stable and consistent wort.
Adequate record keeping will allow for tracking the consistency of the wort. It is very important to
monitor and record as many points as possible such as original gravity, pH, length of boil, percent
evaporation, timing and quantity of hop additions, addition of any coagulants, and any other relevant
data. Good and consistent record makes it much easier to troubleshoot in the event of a problem.
12
Yeast:
Once the equipment is properly cleaned and maintained, the wort is consistent and stable, it is necessary
to ensure that due diligence is rewarded with consistent predictable fermentations resulting in quality
beer.
Yeast performance is tied around different factors. Every step during the brewing process will have an
effect on the yeast that is converting the sweet wort into beer. Once again, good record keeping on the
entire brewing process will help to maintain consistency and to locate inconsistencies that could be
causing a change in yeast performance or beer quality. Pitch rates and oxygenation are inclusive in
determining yeast performance. Adequate pitch rates and oxygenation will help to minimize the impact
of inconsistencies in the brewing process.
(b) Pharmacopoeia
The pharmacopoeia was developed in response to the resolutions of the committee set up for drug
and pharmaceutical quality. The WHO Expert Committee on Specifications for Pharmaceutical
Preparations provided a compendium called Pharmacopoeia. The aim is toprovide easy access to
the information appropriate for manufacturing and monitoring drug quality. They are
supplemented with other material relevant to the quality assurance of pharmaceuticals, some
already issued in the form of WHO documents. The information is presented in logical sequence
as a series of administrative instruments and technical elements of an overall quality assurance
system.
3. (a) Good manufacturing practice is that part of quality assurance which ensures that products
are consistently produced and controlled to the quality standards appropriate to their intended use
and as required by the marketing authorization.
(i) all manufacturing processes are clearly defined. Good manufacturing practices for
pharmaceutical products (GMP)thematically reviewed in the light of experience, and shown to
be capable of consistently manufacturing pharmaceutical products of the required quality that
comply with their specifications;
(ii) qualification and validation are performed;
(iii) all necessary resources are provided, including: (i) appropriately qualified and trained
personnel; adequate premises and space; suitable equipment and services; appropriate materials,
13
containers and labels; approved procedures and instructions; suitable storage and transport;
adequate personnel, laboratories and equipment for in-process controls;
(iv) instructions and procedures are written in clear and unambiguous language, specifically
applicable to the facilities provided;
(v) operators are trained to carry out procedures correctly;
(vi) records are made (manually and/or by recording instruments) during manufacture to show that
all the steps required by the defined procedures and instructions have in fact been taken and that
the quantity and quality of the product are as expected; any significant deviations are fully recorded
and investigated.
(b)Written instructions for self-inspection should be established to provide a minimum and
uniform standard of requirements. These may include questionnaires on GMP requirements
covering at least the following items:
(i) personnel;
(ii) equipment;
(iii) production and in-process controls;
(iv) quality control;
(v) documentation;
(vi) sanitation and hygiene;
(vii) validation and revalidation programmes;
(viii) recall procedures;(ix) complaints management
Section 3
1 (a) Discuss briefly the development of a quality control system in an organization (8 marks)
(b) What are the objectives of quality control programmes? (4 marks)
(c) Discuss the phases of quality control for achieving the objectives of a quality controller.
(11 marks)
14
Soln:
1 (a)
In most establishment, quality control system starts from the planning stage of the product. To design a
product, first step is to produce “master document” in which all the detailed description of the product is
specified. These include:
- Product specification - A list of the raw materials needed to be used and also for the packaging - A complete list of all equipment to be used - Step by step account of all the process by which the product will be made, including the way it is
going to be packed and also where the product is to be delivered. The master document is very important and from this document, a batch production document is
produced which gives a step by step account of how a batch is to be produced. The information on this
document is usually confined to the quality control manager and the production manager. This shows that
the quality control manager is involved in the production right from the onset of the project. (8 marks)
(b)
Objectives of quality control programmes include:
- Reduction of scrap or wastage rate
- Minimization of customer’s complaints and products design
- Increasing the production of non-defective products going to customers
- Maintenance of the desired degree of conformance to product design
- Prevention of defective raw material from getting into production system
- Enhancing the conformance of product performance with customers’ expectation
(4 marks)
(c)
The phases of quality control can be seen under three different framework as follow
A. Product or service quality design
B Production of manufacturing quality
C. Performance quality
15
A. Product or service quality design
Quality must be inherent in the design of the product being flawless, it must call for the use of
better raw material, better choice of manufacturing process and the use of better machines.
Better design of product may take the form of, for example, the use of leather cover instead of
vinyl for a suitcase or car seat. Once quality has been built into a product from the design stage,
higher product quality can be enhanced in subsequent stages.
B Production of manufacturing quality
The fact that better quality has been built into the design stage, the quality of the product can be
better enhanced if efforts are made to manufacture the product with the correct and specified
process and with meticulous adherence to all the engineering details. The quality of the
manufacturing process would be judged by the degree of conformance to this design
specification0.
C. Performance quality
Performance quality is usually a function of the design and manufacturing quality. Performance
quality relates to product’s reliability, functionality and the ease of maintenance and repair
services when requires. It is also a reflection of the extent to which the product’s quality meets
the customers’ expectations. (11 marks)
2 Write short notes on the following: (i) Determination of acceptable loss retention. (4½ marks) (ii) Pharmaceutical elegance test. (4½ marks) (iii) Batch-production records. (4½ marks) (iv) 100% inspection. (4½ marks) (v) Basic manufacturing cost (4½ marks)
Soln: Determination of acceptable loss retention
This involves the determination of the maximum credible before loss that could occur if
everything went wrong. Experience has shown that entire building or production area can be lost
by fire or explosion and it can be estimated how much a company could lose under the most
adverse catastrophic condition. (4½ marks)
16
Pharmaceutical elegance test
This refers to the physical appearance of the dosage units. These standards include inspection to
ensure that solutions are sparkling clear, tablets are not capped of chipped and coloured products
are of the right shade. These standards govern physical quality. (4½ marks)
Batch-production records
This must describe each manufacturing step in detail. The completion of each step or operation
is initiated by the operator. Exact processing temperature, specific mixing times, designated
equipments and precise details of operations, such as mixing sequence, filtration or compression
are carefully specified on the batch-production records. All raw materials are checked for identity
and quality before being incorporated in the process. (4½ marks)
100% Inspection
The question of how many to inspect is basically an economic decision. Inspection may take the
form of 100% inspection of all manufactured products. While this approach can greatly minimize
the chances of passing defective items to the consumers, it is nevertheless, an expensive
approach. The larger the quality of items inspected, the less the cost undetected defective items
but the higher the cost of inspection. (4½ marks)
Basic Manufacturing cost
In consideration of what happens when selecting quality levels, in order to improve quality to get
0% rejects (all parts good) the costs will rise significantly and on the other hand if more rejects
are produced, the economic losses rise. The optimal point to choose where the quality level of
the product will give the optimal economic sense is called Basic manufacturing cost.
(4½ marks)
3 (a) What is a process control chart? (8 marks)
(b) Highlight the daily routine checks in a typical quality control unit in an industrial organization. (5½
marks)
Soln:
3(a) These are charts used in process to monitor the extent of variability in the quality standard of the
finished items from a predetermined standard. It is chiefly used to discover very quickly when the
process is going out of control, i.e when off-standard products are being manufactured. When such
signal is received, the operations manager can act to prevent more sub-standard products from
being produced by taking some corrective actions mentioned above. For those directly responsible
17
for quality control, process control charts have been extremely useful in monitoring the quality
performance of their operations. (8 marks)
Upper Control Limit UCL
Centre Line CL
Lower Control Limit LCL
Figure: Process Control Chart
(b) - Engineering model
- Verification of parts and products
- Standard of quality
- Purchased material control
- Feeder section control
- Assembling and process control
- Completed product, inspection and testing
- Packaging design and
- Verification
- Quality analysis
- Field performance reports and product quality improvement (½ mk each = 5½mks)
18
COURSE CODE: CHM 414 COURSE TITLE: FERTILIZER AND AGROCHEMICALS TUTORIAL QUESTIONS AND ANSWERS
1. With the aid of equations only, show the synthesis of these in the production of fertilizer.
(i) Urea (ii) Super phosphate
2. Using a table show the plant available form, function and deficiency for the following
elements (i) sulphur (ii) calcium (iii) iron (iv) zinc
3. Using a suitable example, explain how the format of reporting nutrient concentrations in
fertilizers is regulated.
4. Discuss the synthesis of phosphorus component with the aid of an equation.
5. Write short notes on the production of multi- component fertilizer.
6. List 3 advantages of organic and slow release fertilizers.
7. Explain the following negative environmental impacts of using fertilizer.
(i) Persistent organic pollutants (ii) Atmosphere (iii) Eutrophication
8. Define the following methods of fertilizer application:
(i) Foliar spraying (ii) Top dressing (iii) Banding
9. A 50 kg bag of fertilizer contains N, P and K at a rate of 40-20-20 respectively.
How many kilograms of N, P and K are in this bag of fertilizer?
10. If a farmer needs to apply fertilizer at a recommended rate of 90+30+60. In the absence of
a complete fertilizer, he was advised to use a combination of three (3) single fertilizers
21-0-0, 0-18-0, and 0-0-60. How much of these combinations should be used to meet the
recommendation?
11. Differentiate between the following:
(i) Pesticide bio-accumulation and pesticide bio-magnification
(ii) Pesticide adsorption and pesticide absorption
12. Explain the pesticide risk factors in the environment.
13. Discuss the pesticide degradation processes.
14. Write short notes on the following pesticides:
(i) Dichlorodiphenyltrichloro ethane
(ii) Lindane
(iii)Parathion
19
15. Mention seven (7) adverse human health effects of organophosphorous pesticides.
16. Discuss how pesticide transfer influences the fate of pesticides in the environment.
17. What are the routes of entry of organochlorine pesticides in surface and ground water?
18. What are pesticides?
19. How would you classify pesticides?
20. Give 17 examples of organochlorine pesticides.
20
TUTORIAL ANSWERS
QUESTION 1
(i) Urea
(ii) Super phosphate
Ca3 (PO4)2+ 3H2SO4+ H2O Ca (H2PO4)2.H2O + 2CaSO4
QUESTION 2
Element Plant Available Forms Functions Deficiencies
Sulphur (S) SO42-
Structural component of some proteins Yellow leaves and stunted growth.
Calcium (Ca) Ca2+ Influences permeability of cell membranes Small develop leaves, wrinkled older leaves & dead stem
tips.
Iron (Fe) Fe2+, Fe3+ & Structural component of a number of Stunted growth & slender, short leaves.
organic complex Fe essential enzymes. Mottled & Interveinal chlorosis in young leaves.
Zinc (Zn) Zn2+ & Component of enzyme for decomposition New leaves are thick & small, retarded growth b/w nodes
organic complex Zn of carbonic acid. Spotted between veins, discolored veins.
21
QUESTION 3
The format of reporting nutrient concentrations in fertilizers is carefully regulated, with on-going
testing of products to verify proper labelling. An analysis that describes the concentrations of plant-
available nutrients can be found on every bag of fertilizer. Generally, there are three numbers that
describe, in order, the concentrations of N-P2O5-K2O. For example, a fertilizer bag of diammonium
phosphate will have the numbers 18-46-0 on it, which means it contains a minimum of 18% N, 46
% diphosphorus pentoxide (P2O5), and no potassium oxide (K2O) by weight.
QUESTION 4
Phosphorus is one of the most essential elements to living organisms and the common industrial
source of phosphorus, is phosphate rock. Phosphate rock consists of accumulated skulls and bones
of marine organisms. It can be used to produce phosphoric acid in two ways. Most of the
phosphoric acid is produced by direct reaction of phosphate rock with tetraoxosulphate (VI) acid.
Ca3
(PO4)2 + 3H2SO4 3CaSO4 +2H3PO4
Alternatively, with less tetroxosulphate (VI) acid, the reaction proceeds only to superphosphate
Ca3
(PO4)2 + 3H2SO4 + H2O Ca (H2PO4)2.H2O + 2CaSO4
Some of these products are reacted further with tetraoxosulphate (VI) acid and trioxonitrate (V)
acid to produce a triple superphosphate, a good source of phosphorous in solid form. Some of the
phosphoric acid is also reacted with ammonia in a separate tank resulting in ammonium phosphate,
another good primary fertilizer.
QUESTION 5
Production of multi-component fertilizer
To produce fertilizer in the most usable form, each of the different compounds namely ammonium
nitrate, potassium chloride, ammonium phosphate and triple superphosphate are granulated and
blended together.
22
Granulation
Granulation involves putting the solid materials into a rotating drum which has an inclined axis.
As the drum rotates, pieces of the solid fertilizer take on small spherical shapes. They are passed
through a screen that separates out adequate size particles. A coating of inert dust is then applied
to the particle; this inert dust prevents the particles from sticking to one another and inhibits
moisture retention. Finally, the particles are dried, completing the granulation process.
Blending
The different types of particles are blended together in appropriate proportions to produce a
composite fertilizer. The blending is done in a large mixing drum that rotates a specific number of
turns to produce the best mixture possible. After mixing, the fertilizer is emptied into a conveyor
belt, which further transports it into the bagging machine.
Bagging
Fertilizer is first delivered into a large hopper and a packing bag is placed on a vibrating surface.
This allows better packing. An appropriate amount is released from the hopper into a bag that is
held open by a clamping device. When filling is complete, the bag is transported upright to a
machine that seals it. The bag is then conveyed to a palletizer, which stacks multiple bags, making
them ready for shipment to distributors.
QUESTION 6
Advantages of organic and slow release fertilizers
Advantages of organic fertilizers
• It improves soil life and long-term productivity of soil.
• Less danger of over-fertilization by adding decomposed organic matter to the soil.
• Organic fertilizers are not easily leached from soil.
• Organic component increase the abundance of soil organisms by providing organic
matter and micronutrients for organisms that aid plants in absorbing nutrients.
Advantages of slow release fertilizers
• Less prone to leaching.
• It enables higher nitrogen use efficiency by plants.
23
• It is less subject to volatilization
• It has lower potential of causing injury to the plants and they can be applied at
higher rates without risk of injury to plants.
QUESTION 7
Negative environmental impacts of using fertilizer
Persistent Organic Pollutants
Toxic persistent organic pollutants (POPs), such as dioxins, polychlorinated dibenzo-p-dioxins
(PCDDs), and polychlorinated dibenzofurans (PCDFs) have been detected in agricultural
fertilizers and soil amendments. POPs are organic compounds that are resistant to environmental
degradation through chemical, biological, and photolytic processes. Their exposure can cause
death and illnesses including disruption of the endocrine, reproductive, and immune systems.
Atmosphere
Methane emissions from crop fields such as rice are increased by the application of ammonium-
based fertilizers; these emissions contribute greatly to global climate change as methane is one
of the potent greenhouse gases.
Eutrophication
Eutrophication is the ecosystem response to the addition of artificial or natural substances, such
as nitrates and phosphates, through fertilizers or sewage, to an aquatic system. It can also be
defined as an increase in the rate of supply of organic matter in an ecosystem. Phosphorus and
nitrogen rich compounds present in fertilizers are carried through runoff, precipitation and
sewages to bodies of water like lakes, rivers, and oceans. This results in nutrient overload,
causing increase in the existence of algae and serious depletion of oxygen in many parts of the
ocean, especially in coastal zones. This depletion of oxygen in the water induces reductions in
specific fish and other marine life, as well as the ability of these areas to sustain oceanic fauna.
Low oxygen conditions can lead to the movement of fish out of affected areas, which eventually
24
leads to reduction of populations of these species, which are not able to tolerate new condition.
Livestock such as cattle can also be at risk of cyanotoxins from drinking water containing high
content of toxic cyanobacterial bloom.
QUESTION 8
(i) Foliar spraying: This is the direct application of micronutrients in solution form on the plant
leaves or sandy soil. It is used to quickly correct nutrient deficiencies. However, if fertilizer
concentration is too high, leaf burning will occur. It is mainly used on citrus fruits.
(ii) Top dressing: is the spreading of fertilizer on the standing crop during the growing season to
improve plant nutrition and boost yields. It is used mainly on small grains, legumes and grasses.
(iii) Banding: This refers to the process of placing fertilizer about 2 inches to the sides and about
2 inches below seed depth. The fertilizer should not be placed directly below seeds to avoid
burning roots. It is usually used on row crops.
25
QUESTION 9
2 5
Nitrogen : ince the label indicates pure nitrogen by weight,
the kilogramsof N in the bag is simply 40% of 50 kg
i.e 40 50kg 100 = 20 kg.
Phosphorous : The 20% on the label means 20% of P O by weight
S
2 5
not just P.
First, calculate how much P is in the bag and then calculate the kg.
Molecular weight of P 31 grams / mole
Formula weight of P O (31 2 16 5) 142 grams / mole
62 g / m 142 g / m 43% P
2 5
2 5
2
in P O
43% P x (0.20 or 20% by weight of P O
8.6% P in the bag of fertilizer
8.6% P x 50 kg 4.3 kg of P in the bag
Potassium : Also the 20% on the label means 20% of the K O by weight not just
2
K.
So, we first calculate how much K is in the bag and then calculate the kg.
Molecular weight of K 39 grams / mole
Formula weight of K O 94 grams / mole
39 x 2 78 grams / mole 94 grams / mole
0.83
2
2
83% K in K O
83% K x 0.20 or 20% by weight of K O
16.6% K in the bag of fertilizer
16.6% K x 50 kg 8.3 kg of K in the bag
26
QUESTION 10
Amount of fertilizer material kg
Recommendation rate kg nutrient / hactre x Area ha
% Nutrient in fertilizer material.
To calculate the amount of fertilizer materials for 1ha
@ the recommended rate of 90
30 60.
Using a combination of single fertilizers:
·
·
·
90 / 1 ( ) = 428.6
0.21
0 1
Kg N ha haAmount of Kg
Amount of
21 0 0 ammonium Sulphate
0 18 0 Ordinary Superphosphate
0 0 60 Potassium Chloride
21 0 0
2 5
2
30 P O / 18 ( ) = 166.7
0.18
60 K O / 1 0 6 ( ) = 100.0
0.60
428.6 166.7 100.0 695.3
, 428.6 21 0 0,166.7 0 18 0
100.0 0 0 60
Kg ha haKg
Kg ha haAmount of Kg
Therefore the farmer must apply Kg Kg
and Kg to satisfy the recommendat
0
0 0
90 30 60.
ion rateof
27
QUESTION 11
(i) Pesticide bio-accumulation refers to the ability of pesticides to build up in the body tissue of
animals.
Pesticide bio-magnification refers to the build up of pesticides across the food chain.
(ii) Pesticide absorption is the movement of pesticides into plants and animals or structures such as
soil and wood. Once absorbed by plants, pesticides may be broken down or they may remain in the
plant until tissue decay or harvest. Absorption of pesticides by target and non target organisms is
influenced by environmental conditions, physical and chemical properties of the pesticide and the soil.
Pesticide adsorption refers to the binding of pesticides to soil particles and organic matter. Positively
charged pesticide molecules are attracted and bound to negatively charged clay particles. The amount
of adsorption in the soil depends on the type of soil, the soil conditions (temperature, pH, moisture
content etc) and the characteristics of the pesticides. Soils high in organic matter or clay are more
adsorptive than coarse, sandy soils, in part because a clay or organic soil has more particle surface area
onto which pesticides can bind. Moisture affects adsorption. Wet soils tend to adsorb less pesticide than
dry soils because water molecules compete with the pesticide for the binding sites. Pesticides vary in
their adsorption to soil particles. Pesticide adsorption leads to reduced pest control hence higher
application rates are recommended when the chemical is applied to adsorptive soils.
QUESTION 12
The use of pesticides introduces some risk to the environment. The degree of risk depends upon four
factors namely persistence, mobility, non-target toxicity and volume of use. Thus, environmental risk is
minimized when any of the risk factors is close to zero.
Persistence
Persistence describes how long the active ingredient of the pesticide remains active in the environment.
A pesticide that remains active in the environment for a long period of time is described as persistent.
The more persistent a pesticide is, the higher the risk to the environment.
Mobility
Mobility refers to the ability of the active ingredient of the pesticide to move away from the site of
application through the soil, water or air. The more easily the pesticide is able to move away from the
site of application, the higher the risk to the environment.
28
Non-target Toxicity
Non-target toxicity refers to the unintended harmful effect of the pesticide on any organism other than
the pest. The risk to the environment increases if the non-target toxicity of the product is high.
Volume of Use
Volume of use refers to the total amount of pesticides used in the environment. The larger the
amount of product used in the environment, the higher the potential will be for environmental
damage.
QUESTION 13
Pesticide degradation refers to the breakdown of pesticides in the environment. The rate at which the
degradation occurs is measured by the pesticide’s half-life. Pesticide degradation is usually beneficial as
pesticide-destroying reactions change most pesticide residues in the environment to non toxic or
harmless compounds. However, degradation is detrimental when a pesticide is destroyed before the
target pest has been controlled. The rate of pesticide degradation is affected by many environmental
factors including temperature, moisture and pH. The three types of pesticide degradation are microbial,
chemical and photodegradation.
Microbial Degradation
This is the breakdown of pesticides by fungi, bacteria and other microorganisms that use pesticides as
a food source. It is the most common type of pesticide breakdown. Pesticides are broken down into
basic compounds such as water and carbon (IV) oxide. Most microbial degradation of pesticides occurs
in the soil. Soil conditions such as moisture, temperature, aeration, pH and the amount of organic matter
affect the rate of microbial degradation because of their direct influence on microbial growth and activity.
The frequency of pesticide application is also a factor that can influence microbial degradation. Rapid
microbial degradation is more likely when the same pesticide is used repeatedly in a field. Repeated
applications can actually stimulate the build up of organisms that are effective in degrading the chemical.
Microorganisms greatly reduce the effectiveness of these chemicals soon after application. The
possibility of very rapid pesticide breakdown is reduced by using pesticides only when necessary and by
avoiding repeated applications of the same chemical.
Chemical Degradation
29
This is the breakdown of pesticides by processes that do not involve living organisms. It is the chemical
reaction that occurs between the pesticide and other chemicals in the environment resulting in the
splitting of pesticides into less hazardous compounds. The adsorptive capacity, pH, temperature,
moisture, mineralogy of the soil, physical and chemical properties of the pesticide determine the rate
and type of chemical reactions that occur. One of the most common pesticide degradation reactions is
hydrolysis, a breakdown process in which the pesticide reacts with water.
Photodegradation
This is the breakdown of pesticides by ultraviolet or visible light, particularly sunlight. Photodegradation
can destroy pesticides on foliage, surface of the soil and in the air. Pesticides, once applied, vary
considerably in their stability under natural light. Factors that influence this kind of degradation include
intensity of the sunlight, characteristics of the application site such as soil type and vegetation;
application method, physical and chemical properties of the formulated pesticide. Pesticide losses from
photodegradation can be reduced by incorporating the pesticide into the soil during or immediately after
application and by using adjuvants in the pesticide formulation to protect the active ingredient from
photodegradation.
QUESTION 14
(i) Dichlorodiphenyltrichloro ethane (DDT)
Dichlorodiphenyltrichloro ethane (DDT) was first synthesized in 1874. It is an organochlorine
insecticide commonly used for the control of disease-bearing insects and on a variety of food crops.
It has been banned from use in most nations because of its potential for human toxicity and severe
ecological effects. Although DDT has not been used in most nations for decades, it is still found
as a contaminant because of its extreme persistence and high mobility in the environment. It is still
sprayed indoors in some developing countries for malaria vector control. In the environment and
in the body, Dichlorodiphenyltrichloro ethane (DDT) breaks down into Dichlorodiphenyl ethane
(DDE) and Dichlorodiphenyldichloro ethane (DDD) over time. The most common route of DDT
exposure is through diet, particularly fatty foods such as fish, meat and diary products. DDT is
known to adversely affect the nervous system and DDT and its metabolites, DDE and DDD, could
interfere with normal reproduction and development as a result of its endocrine disrupting
properties. They have been classified as probable human carcinogens. The continued use of DDT
in some countries contributes to worldwide environmental contamination and can accumulate to
30
high levels in soil, sediment, plants, animals, fish and humans. Analysis of blood and urine are the
most common methods for detecting DDT exposure. It can also be measured in fatty tissues and
breast milk. DDE has the shortest biological half–life followed by DDT and then DDD. It is the
persistence of DDT and its breakdown products that leads to its bioaccumulation and bio-
concentration in the food chain.
(ii) Lindane
Lindane is a restricted pesticide used to treat seeds (barley, corn, oats, rye, sorghum and wheat)
prior to planting and as a pharmaceutical agent for control of head lice and scabies. Because of its
persistence and widespread use in the past, it still contaminates the environment, including the
human food supply. It is highly persistent in the environment and can remain in soil and sediment
for extended periods, accumulating in plants, fish and animals consumed by humans. Dietary
exposure is the most common route of lindane exposure. Its exposure can cause a wide range of
adverse health effects in humans including neurological effects, liver toxicity, reproductive and
developmental effects. Exposure to high doses can cause symptoms such as vomiting, nausea,
diarrhea, muscle weakness, seizures, blood disorders and immune deficiencies. Studies have also
shown possible associations between lindane exposure in pregnant women and increased risk of
spontaneous abortion and premature delivery. Lindane is rapidly broken down and excreted from
the body. Lindane and its metabolites can be measured in serum, urine and other body fluids and
tissues.
(iii) Parathion
Parathion is an organophosphate compound. It is a very potent insecticide and an acaricide. It was
originally developed by Farben in the 1940s. Parathion is soluble in alcohols, esters, ethers,
ketones, and aromatic hydrocarbons but is insoluble in water, petroleum ether, kerosene or spray
oils. Parathion is stable at a pH below 7.5. It is highly toxic to non-target organisms and its use is
banned or restricted in many countries. In its purest form, parathion consists of white crystals.
However, more commonly distributed forms take the form of a brown liquid which smells of
rotting eggs or garlic. As a pesticide, parathion is applied by spraying, and often used on cotton,
rice and fruit trees. The usual concentrations of ready-to-use solutions are 0.05 to 0.1%. The
chemical is banned for use on many food crops. Parathion is a cholinesterase inhibitor and disrupts
neural function by inhibiting the essential enzyme acetylcholinesterase. It is absorbed through the
31
skin, mucous membranes, and orally. Absorbed parathion is rapidly metabolized to paraoxon in
which the sulphur atom is replaced by oxygen. Paraoxon exposure can result in headaches,
convulsions, poor vision, vomiting, abdominal pain, severe diarrhea, unconsciousness, tremor,
dyspnea and lung-edema as well as respiratory arrest. Parathion is considered to be a possible
human carcinogen. It is toxic to fetuses, but does not cause birth defects.
QUESTION 15
Neurotoxicity, development/reproductive harm, endocrine disruption, nausea, headaches,
twitching, trembling, excessive salivation and tearing, convulsions and death.
QUESTION 16
Pesticide Transfer
Pesticide transfer is essential for pest control as some pesticides need to circulate for effective utilization.
Pesticides can be transferred through natural processes such as volatilization, runoff, leaching,
absorption and crop removal.
Volatilization
This is the conversion of a solid or liquid into a gaseous state. Once volatilized, a pesticide can move in
air currents away from the treated surface. The higher the vapour pressure, the more volatile the
pesticide. Environmental factors such as high temperature, low relative humidity and air movement tend
to increase volatilization. A pesticide tightly adsorbed to soil particles is less likely to volatilize. Soil
conditions such as texture, organic matter content and moisture can thus influence pesticide
volatilization. Volatilization can result in reduced control of the target pest because less pesticide remains
at the target site. Vapour drift can lead to injury of non target species. To avoid pesticide volatilization,
application of volatile pesticides when conditions are unfavorable should be avoided. Low-volatile
formulations should also be employed.
Runoff
32
This refers to the movement of water over the land surface or a sloping surface. It occurs when
water accumulates on the land surface faster than it can infiltrate the soil. Pesticides can be carried
in the water itself or bound to eroding soil particles. The amount of pesticides in runoff water is a
function of site-related factors such as the slope of the land and moisture content of the soil.
Climatic factors such as temperature, the amount and timing of rainfall relative to the pesticide
application are also of influence. Climatic factors affect the persistence of pesticides in the
environment thus influencing the availability of pesticides for transport by runoff. Other factors of
note are the pesticide-water-soil interactions such as the solubility and adsorptivity of the pesticide,
the erodibility and texture of the soil. Pesticide runoff is usually greatest after an application.
Pesticide runoff can lead to groundwater contamination and can cause injury to crops, livestock or
humans if the contaminated water is used downstream.
Leaching
This is the movement of pesticides through the soil rather than over the surface. Pesticides can leach
downward, upward or side to side. Leaching depends on the pesticide’s chemical and physical properties
such as adsorption, solubility and persistence. A pesticide held strongly to soil particles by adsorption is
less likely to leach. A pesticide that dissolves in water can move with water in the soil. A pesticide that
is rapidly broken down by a degradation process is less likely to leach because it may remain in the soil
only for a short time. Soil factors that influence leaching include permeability, texture and organic
matter. The more permeable a soil, the greater potential for pesticide leaching.
Absorption
This is the movement of pesticides into plants and animals or structures such as soil and wood.
Absorption of pesticides by target and non target organisms is influenced by environmental conditions,
physical and chemical properties of the pesticide and the soil.
Crop Removal
Crop removal transfers pesticides and their breakdown products from the treatment site. Most harvested
food commodities are subjected to washing and processing procedures that remove or degrade much
of the remaining pesticide residue. Pesticides can be transferred during operations such as tree and
shrub pruning and turf grass mowing.
33
QUESTION 17
Organochlorine pesticides can enter surface and ground water via these processes
1. Natural processes including run off, leaching and erosion
2. Spray and vapour drift during application
3. Using more pesticide than is recommended on the label
4. Container leaks and flooding while pesticides are in storage
5. Back siphoning of pesticides from the spray tank into wells during tank filling
6. Overflow of spray tanks during filling
7. Waste water from equipment clean up
8. Improper disposal of excess spray mix, unwanted waste pesticides and pesticide containers
9. Atmospheric fall out (rain or snowfall containing pesticides)
QUESTION 18
Pesticides are chemicals – liquids, granules or gases – used to kill or control pests such as insects,
weeds, bacteria, fungi, rodents and worms.
QUESTION 19
Pesticides can be classified according to chemical class such as organochlorine, carbamate,
organophosphorus, chlorophenoxy compounds. It can also be classified according to their
intended use example insecticide, herbicide, rodenticide, fungicide, fumigant and acaricide.
QUESTION 20
Examples of organochlorine pesticides are DDT, chlordane, lindane, aldrin, dieldrin, toxaphene,
heptachlor, endosulfan, dicofol, methoxychlor, hexachloro benzene (HCB), mirex,
pentachlorophenol (PCP), beta-hexachlorocyclo hexane, trans-nonachlor, heptachlor epoxide and
pentachlorophenol, 2,3,5-trichloro phenol.
34
COURSE CODE: CHM 416 COURSE TITLE: DETERGENT AND COSMETIC CHEMISTRY
1. a) What are surfactants? (5 marks) b) Alcohols are typical examples of non-ionic surfactants. Discuss, with appropriate examples,
their chemical and physical properties, uses, stability and safety. (13 marks)
c) List 5 examples of oral hygiene cosmetic products. (5 marks)
2. a) Acyl glutamates are typical examples of anionic surfactants. Discuss with appropriate
examples, their chemical and physical properties, uses, stability, and safety. (13 marks)
b) Highlight the various factors responsible for the dynamic expansion of the cosmetics industry
worldwide. (3 marks)
3. Ester carboxylic acids are a sub-group of surfactants. Discuss with appropriate examples, their
chemical and physical properties, uses, stability and safety. (13 marks)
4. a) What is a cosmetic substance? (5 marks)
b) List 6 basic raw materials used in the manufacture of skin creams. (4 marks)
5 a) Write a formulation for the production of a typical body cream. (5 marks)
b) With the aid of a flow diagram, fully classify cosmetics according to their areas of
application. (7 marks)
c) Write a general formula for an alkyl sulphate used as a detergent (2 marks)
6. In the evalution of cosmestic substances many parameters come into play. In tabular form state the test parameters for the following products:
(i) powders.
(ii) perfumes, anti-perspirants, deodorants;
(iii) lotions, creams, jelly, pomades, ointments;
35
(iv) soap-bar, syndet or flakes;
(v) detergent, shampoo, foam bath. (10mks)
7. Explain the chemistry of soap making. (10mks)
8. Write short note on the following;
Soap
Detergent
Fat and oil
Alkali
Emulsifying agent
Micelles
9. In detergent making what is the application of magnesium sulphate and lipids, and how does
surface tension come into place. Explain showing equation of reaction,
SOLUTION
Question 1
(a)
Surfactants are surface-active agents widely used in cosmetic products especially in shampoos, dentrifices, etc.
These compounds are characterized by foam production and reduction of surface or interfacial tension. They
are amphiphilic in nature, and comprises of both a lipophilic and hydrophilic component. These amphiphilies
form oriented films at interfaces and function primarily as detergents foaming or wetting agents, emulsifiers,
solublizers or dispersants. (5mks)
(b)
Chemical Properties
Surfactant types of alcohols are the hydroxyl derivatives of long chain alkane hydrocarbons. These alcohols
exhibit the classic surface and inter facial alignment behaviour of surfactants but their essential water insolubility
is the reason for their inclusion only as coemulsifiers.
Only primary alcohols having carbon chain ranging from about 8 to 18 exhibit useful surfactant properties.
The presence of a second hydroxyl group, for example in lanolin alcohols, enhances the alcohol cosmetics utility.
Most surfactants alcohols were initially obtained by hydrogenation of the corresponding natural fat ty acids
and therefore contained an even number of carbon atoms. Alcohols are now also prepared by synthetic process.
The Ziegler process yields even numbered straight chain alcohols.
The oxo process yields even and odd numbered alcohols that may exhibit some branching and presence of
36
secondary alcohols. The properties of these alcohols differ and their further use in the manufacture of
surfactants of raw materials makes this distinction significant. Most commercially available alcohols are
mixtures of homologues. The alcohols are chemically inert and do not undergo reactions during the preparation
of cosmetic products.
Physical Properties
The alkanols comprising this group are generally waxy solids or liquids depending on their purity. They
tend to crystallize in finished emulsions unless they are carefully formulated.
Uses :Alcohols have been found to perform their surfactant function primarily in the presence of a second
surfactant. Depending on the concentration employed, they are emulsion stabilizers, opacifiers, viscosity
increasing agents and foam boosters.
Stability :Alcohols are chemically stable in cosmetic products.
Safety :Alcohols of the surfactant type are regarded as safe for use in cosmetics.
Examples: R-CH2-OH
1. Cetyl alcohol CH3(CH2)15OH
IUPAC 1-Hexadecanol. It serves as surfactant in shampoos, emollient, emulsifier or thickening agent in creams
and lotions.
2. stearyl alcohol CH3(CH2)17OH
3.
(13mks)
(c) toothpastes, toothpowders, solid dentifrices, denture cleaners, mouthwashes, gargles. (5mks)
Question 2
a)
The Acyl Glutamates
The Acyl Glutamates belong to Alkylamino Acids group. Surfactants in this group are prepared by the acylation of the amino group of a-amino acids. This is conducted primarily with naturally occurring fatty acids. During the acylation, the amino groups of the amino acids are neutralized and the resulting products are anionic surfactants.
Acyl Glutamates are derived primarily from glutamic acids and this sub-group includes some aspartic acid derivatives. 2mks
Chemical Properties
Glutamic acids is a dicarboxylic acid and its N-acyl derivative, can form mono or disalts with alkalies. The aqueous solutions of the mono-salts are slightly acidic (pH 5-6), while the disalts are alkaline. Both salts are readily soluble in water. The chirality of the a-amino group is generally specified as the L-form, that is, that of the natural amino acids. The acyl glutamates are amides and may undergo hydrolysis under adverse pH conditions. 2mks
Physical Properties
HO
LAURYL ALCOHOL
37
The sodium salts are solids, while the TEA salts are generally marketed as 30% aqueous solutions. The acylglutamates foam relatively poorly 1mk
Uses
The acylglutamates are used in skin cleansing products and shampoos, because of their general mildness. 2mks
Stability
The acylglutamates are amides but evidently possess adequate resistance, to hydrolysis in cosmetic products. The amphoterics in this group possess an amido group that may be hydrolyzed at extreme pH conditions. Because such conditions are not encountered normally in cosmetic products and procedures, They are considered stable. 2mks
Safety
Glutamates as a group are non-irritating and non-sensitizing. The mildness of these surfactants is concentration-dependent and may cause eye irritation in concentration solutions (above 20%). At more normal concentration, they are well tolerated by skin and mucous membranes. 2mks
Example with structure : Sodium acylglutamate
HOOC CH2CH2CH COONa
NH C
O
R
2mks
TOTAL = 13MKS
Question 3
Chemical Properties: Ester carboxylic acids are a small group of monoesters of di- or tri-carboxylic acids.
The ester may be formed by an alcohol and polycarboxylic acid (dinonoxynol-9 citrate) or by an acid that
react with a hydroxyl group on the carboxylic acid (acyllactylates). The ester- group is subject to hydrolysis
under adverse pH conditions.
The most important carboxylic acid is lactyl lactic acid, that is, the ester formed between two molecules
of lactic acid. This esterification is likely not to go to completion, which leaves lactic acid as one
impurity or produces polylactylates as additional impurities. 5mks
Physical Properties
The ester carboxylic acids and waxy solids salts of the short chain lactylates foam well. It
has been found to be substantive to hair and provide humectant qualities. 2mks Uses
The ester carboxylic is useful o/w and w/o emulsifies. They can be used in shampoos,
depending on their foaming ability. 2mks
38
Stability
The members of this group are esters but are considered stable under cosmetic use
conditions. 1mk Safety
Ester carboxylic acids are reported to be mild on the skin. 1mk
Examples
i) Di non-oxynol-9 citrate
ii) Sodium Acyl lactylate 2mks
Total =13mks
Question 4
a)
b) (i) water,( ii) petroleum oil (iii) vegetable oils, fats (iv) waxes (v) humectants
(vi) emulsifying agents (4mks)
Question 5
(a) Annotated flow diagram (7 mks)
(b)
OR
(2 mks)
C
H
R O SO3 Na
R
SO3 Na
39
COURSE CODE: CHM 418
COURSE TITLE: NATURAL PRODUCTS
1. (a) Write the chemical structures of the following alkaloids (i) quinoline (ii) pyridoxine (vitamin B6) (iii) piperidine (iv) caffeine. (6 marks)
(b) The synthesis of thiamine chloride hydrochloride has been used commercially for the production of
thiamine (Vitamin B1). Outline the synthesis. (13 marks)
(c) Give one health problem that each of the following vitamins will prevent:
(i) Vitamin D (ii) Vitamin B1 (iii) Vitamin B2 (iv) Vitamin K (4 marks)
2. (a) With the aid of chemical equations explain the synthesis of vitamin A1. (10 marks)
(b) Write the chemical structures of α-tocopherol (vitamin E), shikimic acid, morphine and
cinnamic acid. (4 marks)
(c) Alkaloids are secondary metabolites and are prominent in medicinal chemistry. List any four
classes of alkaloids (4 marks)
3. (a) Give three examples of lupine alkaloids. (3 marks)
(b) Complete the reactions below: (6 marks)
(c) Illustrate fully the biosynthesis of papaverine and laudanosine. (14 marks)
4. (a) Show the complete biosynthesis of coniine from ethanoic acid. (8 marks)
nicotine? ?
O2
Vanadium
? AlCl3
CH3Cl N
?NH3
N
CONH2
CO(NH2)2
40
(b) Suggest an appropriate mechanism for the total synthesis of Tropinone A, starting with glyoxal.
(10 marks)
H3C
N
O
A
(i) The first insect pheromone was discovered in 1959. Many other pheromones were isolated later
because of their wide applications. Itemize three (3) main uses of pheromones. (3 marks)
(ii) Give two examples of pheromones that occur in nature. (2 marks)
5. (a) Illustrate fully the biosynthesis of nicotinic acid. (6 marks)
(b) Distinguish between and –ionones in terms of their degradation products. (6 marks)
(c) Give seven (7) examples of alkaloids derived from anthranilic acid. (5 marks)
(d) On ozonolysis, ocimene [C10H16] produces formaldehyde, methyl glyoxal, laevualdehyde, acetic
and malonic acids and acetone. Illustrate this reaction with an equation. (6 marks)
6. (a) Classify alkaloids,giving an example in each case.
(b) Outline by means of chemical equations the reaction of nicotine (fig.1) with:
(i) KMnO4 (ii) ZnCl2 (iii) HI.
N
N
Nicotine Fig. 1
(c) Using only chemical equations give an account of the biosynthesis of structure A from
structure B.
41
NH
NCH
3O
CH3A
NH
NH2
COOH
B
(d) What can you deduce from the reaction of morphine with
(i) acetic anhydride, py
(ii) hydrogen/Pt.then oxidation
(iii) NaOH
(iv) CH3I
(v) HI
(vi) Me2SO4
7. (a) Metabolism via the shikimate pathway gives rise to a large number of aromatic compounds.
Outline the shikimic acid pathway for the formation of C6-C3 unit metabolites.
b) Give examples of six major subgroups of flavonoids.
8. (i) Predict the products formed when limonene reacts with the following reagents:
limonene
a) Excess HBr (3
marks)
b) Excess bromine, Br2, in CCl4 (3
marks)
c) Ozone followed by dimethyl sulfide (3
marks)
42
(ii) Carefully circle the isoprene units in the following terpenes and label each compound as
monoterpene, sesquiterpene or diterpene. (8.5
marks)
OOH
H
OH
carvone patchouli alcohol
cedrene tetrahymanol
-bisabolene
9. Complete the following reaction:
+
CatalysisNa/Hg
CHO
CrO3O
H2CH2OH
?
?
43
SOLUTION
Question 1
a)
(6mks)
b). Step i)
N
NHO
HO OH
pyridoxine
NH
piperidine
O
N
N
NN
O
caffeine
(i) (ii)
(iii)
(iv)
Quinoline
44
CO2C2H5
CH2CH2OC2H5
+ HCO2C2H5
Na
CO2C2H5
CHCH2OC2H5
CHO
CH3C
NH2
NH
C2H5ONa
4mks
N
N
OH
CH2OC2H5
H3C
i) POCl3
ii) NH3-C2H5OH
N
N
NH2
CH2OC2H5
H3C
N
N
+NH3
CH2Br
H3C
HBr
Br-
3mks
Step ii)
N
N
+NH3
CH2Br
H3C
Br-
+
N
S
CH3
CH2CH2OH
N+
S
CH3
CH2CH2OH
N
N
+NH3
CH2
H3C
Br-
Br-
4mks
N+
S
CH3
CH2CH2OH
N
N
+NH3
CH2
H3C
Cl-
Cl-
AgCl in
CH3OH
2mks Total = 13marks
(c) (i) rickets (ii) beriberi (iii) premature aging (iv) hemorrhaging (3mks)
Question 2
a) (a)
45
O
NaN
H 2
MeI
O
Na/NH3
OH i) EtMgBr
ii)O
OH OH
I
H+
rearr.
OH
CH2OHi)LiAH
ii) AC2O
OH
CH2OAcIII
II
i)TSOH(-H2O)
ii) OH-
OH
CH2OH
VITAMIN A1
46
10mks
(i) α-tocopherol
1mk
(ii) Shikimic acid
1mk
(iii) Morphine
COOH
OH
OH
HO
O OH
alpha tocopherol C29H50O2
HO
O
HOH
N
47
1mk
(iv)
1mk
(c) phenylethylamine, pyrrolidine, pyridine and piperidine, quinoline, isoquinoline, indole, lupine (any
four)
Question 3
3 (a) Examples of Lupine alkaloids
3(b)
OHO
cinnamic acid
48
N
N
N
Nicotinic acid
Nicotine
N
N N
CH3
H
COOH
CONH2
CH3
AlCl3
CH3Cl
KMnO4
O2
Vanadium
CO(NH2)2
NH3
N
COCl
3(c) Biosynthesis of papaperine
MeO
MeO
HCHO
HCl
MeO
MeO
MeO
MeO
CH2Cl
KCN
MeO
MeO
CH2CN
MeO
MeO
MeO
MeO
MeO
MeO
Cl
O
NH2:
BaseHeat
H2/Ni1)H3O+
2) PCl5
MeO
MeO N H
C O
POCl3
CH3CN
MeO
MeON
MeO
MeON
MeO
MeON
MeO
MeO
MeO
MeO
-H2
Pd/ asbestos
heat
Imine
1) HCHO
2) NaBH4reduction
Papaverine
A
B
A + B
Laudanosine
49
Question 4
4(a)
4(b)
CHO
CHO
+ CH3NH2N
OH
CH3
+ COOH
COOH
O
CO2N CH3
+H2C
COOH
O
CO2
N
O
H3C
50
4 (c) (i)
It is used as sex attractant in perfumes and perspirants. It can be used to determine which insect pests are present in a crop field. It can be used for mating disruption. It is used in regulation and synchronization of human menstrual cycle. The commonest use is still for prognosis.
……. Any three for (3mks)
(ii) exo-brevicomin, disparlure, 3-methyl-4-octanol, sulcatol,
Japonilure, serricornin, 4,8-dimethyldecanal.
…….. any two for (2mks)
5. (a)
5. (b)
Biosynthesis of nicotinic acid
2. Cyclization1. [NH2]
NNicotinic acid
COOH
O H
HO
OP
+
N
CH2
PLP
COOH
H
HO
N
CH2
PLP
COOH
51
O
B ionone
[O]O
CO2H
Geronic acid
+
CO2H
CO2HCO2H
2,2-Dimethyl succinicc acid2,2-Dimethyl adipic acid
+
O
[O]
O
+ CO2H
CO2HCO2H
2,2-Dimethyl glutamic acid3,3-Dimethyl adipic acid
+
CO2H
CO2H
isogeronic acid
(c)
(d)
2CH2O
+ +
O
+
CHO
CHO
CH3COOH
I
COOH
COOH
CH2
52
Question 8
a) Excess HBr (3 marks)
Br
Br
H
b) Excess bromine, Br2, in CCl4 (3 marks)
Br
Br
Br
Br
c) Ozone followed by dimethyl sulfide (3 marks)
O
O
O
OH
H
d) Carefully circle the isoprene units in the following terpenes and label each
compound as monoterpene, sesquiterpene or diterpene.
(8.5 marks)
53
OOH
H
OH
-bisabolene
sesquiterpene
carvone
monoterpene
patchouli alcohol
sesquiterpene
cedrene
sesquiterpene
tetrahymanol
diterpene
54
COURSE CODE: CHM 431 COURSE TITLE: POLYMER CHEMISTRY
Section 1
1. Differentiate between end-to-end distance and distance of gyration- statistical parameters for
polymer dissolution.
2. Mention two (2) Thermodynamic factors for polymer dissolution.
3. Write the kinetics of Living Anionic Addition Polymerization.
4. Compare ionic polymerization with free radical polymerization.
5. Discuss five (5) determinants of polymer dissolution.
6. Give five (5) examples of fibre forming polymers.
Solution to Section 1
1. End-to end distance represents the average distance between the first and the last segment
of macromolecules, it ranges between a maximum value and a minimum value, while Radius
of Gyration is the average distance in linear polymers , with a large number of ends.
Or
The radius of gyration is the square mean radius of each one of the elements of the chain
measured from its centre of gravity.
2. Gibbs free energy (∆G) and the solubility parameters.
3. In general, the reaction mechanism for living anionic addition polymerization are as follows:
where I = initiator, kinit = the initiation reaction rate constant, M = monomer, M-= propagating species, and kprop = the propagation reaction rate constant.
As most polymerizations of this type do not have a termination pathway, the rate of polymerization is the rate of propagation:
where kp is the rate of constant of propagation, [M-] is the total concentration of propagating centers, and [M] is the concentration of monomer. Since there is no termination pathway in living
55
polymerizations, the concentration of propagating centers is equal to the concentration of initiator ([I]). Thus,
The degree of polymerization, Xn is also affected by no termination pathway. It is the ratio of concentration of reacted monomer ([M]o) to initiator([I]o) times the percent conversion p. In this case, the chain length (ν) is equal to Xn.
When conversion, p = 1 (100% conversion), chain length is simply the ratio of reacted monomer to initiator.
Termination due to Impurities
When termination occurs due to impurities, the impurities must be taken into account in determining
the reaction rate. The reaction mechanisms would begin the same as that of a living anionic addition (initiation and propagation). However, there would now be a termination step to account for the effect of the impurities on the reaction.
where M-= propagating species, HX = impurity and kterm = the termination reaction rate constant.
Using the steady-state approximation, the rate of propagation becomes
Since
Thus chain length and rate of propagation are negatively impacted by the presence of impurities in the
reaction.
5. (i) In free radical polymerization the characteristics of the active centres depend only on
the nature of the monomer and are generally independent of the reaction medium, in
56
ionic polymerizations the polarity of the solvent strongly influences the mechanism
and rate of ionic polymerization.
(ii) Ionic polymerization involves successive insertion of monomer molecules between
an ionic chain end (positive in cationic and negative in anionic polymerization) and a
counter ion of opposite charge.
(iii) Unlike free radical polymerization, ionic polymerization is associated with what may
be termed as monomer selectivity.
6. The dissolution of polymer is determined by the following factors:
The degree of cross linking Polarity Branching Crystallinity of polymer Molecular weight
THE DEGREE OF CROSS LINKING
In reaction to solubility, as the degree of cross linking of a polymer increases, the solubility of that
polymer decreases because the strongly linked polymers would subdue the reaction between the
polymer chains and the molecules of solvent. i.e. as the degree of cross linking increases, the solubility
of polymer decreases. The strongly cross linked polymers will inhibit the interaction between polymer
chains and solvent molecules preventing those polymer chains from being transported into solution.
MOLECULAR WEIGHT
In a given solvent, at a particular temperature, as the molecular weight increases the solubility of the
polymer decreases, i.e. the higher the molecular weight, the lower the solubility of a polymer. Thus,
Molecular weight and entanglement slow down motion of polymers.
BRANCHING
Branched polymer chains increase the solubility of polymer, though the rate is dependent on the type of
branch displayed. Polymers with long chain tend to dissolve slowly than the branched polymer. (1 mark)
CRYSTALLINITY
This is the property of a polymer which describes regularity in shape. Crystalline polymers are mostly
regular in shape and three dimensional in structure. Monomers of crystalline molecules form crystal
lattice. Solubility of a polymer decreases with increasing crystallinity. The solubility can be forced if the
appropriate solvent is available, or warming the polymer up to temperature slightly below its crystalline
melting point (Tm). For example, highly crystalline linear polyethylene (Tm = 1350C) can be dissolved in
57
several solvents above 1000C. Nylon 6,6 (Tm = 2650C) a crystalline polymer which is more polar than
polyethylene can be dissolved at room temperature in the presence of solvents with enough ability to
interact with its chain through hydrogen bonds.
POLARITY
Polar polymers are soluble in polar solvent while non polar polymers are soluble in non polar solvents.
Polar polymer such as poly acrylic acid, poly amide and polyvinylalcohol are soluble in water.
c. Fibre forming polymers
Polymers of unsaturated hydrocarbons Polymers of hydroxyl compounds.
Polymers of aldehyde, ketones and oxides. Polymers of unsaturated hydrocarbons
Polyanhydrides polyesters polyamides heterocyclic polymers
Nylon, olefin, polyester acetate, triacetate, acrylic, modacrylic, spandex, and vinyon
polyethylene and aramid fibres.
Section 2
1 (a) What is polymer chemistry? (2 marks)
(b) What do you understand by the following terms in polymer science?
(i) Crosslinking (ii) Elastomers (iii) Plasticizer
(iv) Branched polymer (v) Alteration (vi) Functionality (2 marks each)
(c) Discuss polymer classification under the following headings:
(i) Chain identification (ii) Reaction mode (iii) Physical property related to heating
Soln:
1(a)
58
Polymer chemistry is a multidisciplinary science that deals with the chemical synthesis and
chemical properties of polymers or macromolecules. According to IUPAC recommendations,
polymers describe the bulk properties of polymer materials and belong to the field of polymer
physics as a subfield of physics. (2 mks)
(b)
Crosslinking – A process in which bonds are formed by joining adjacent molecules. At low density,
these bonds add to the elasticity of the polymer and at higher densities, eventually produce rigidity
in the polymers. (2 marks)
Elastomers – A class of polymers that have some degree of Crosslinking and are rubbery. Elastomers
possess memory, i.e. they return to their original shape after a stress is applied. (2 marks)
Plasticizer - Material added to a polymer to improve its processability and/or flexibility. These are
low molecular weight substances which, when mixed with a polymer, lower its glass transition
temperature, Tg. (2 marks)
Branched polymer - A polymer with a chemical side chain extending from the main backbone.
(2 marks)
Alteration - This entails changing the molecular structure of molecules in one fraction to that of
another i.e. rearranged. One of the processes used is called alkylation. In alkylation, low molecular
weight compounds, such as propylene and butylene, are mixed in the presence of a catalyst such as
hydrofluoric acid or sulphuric acid. (2 marks)
Functionality - In any reaction resulting in the formation of a chain or network of high molar mass,
the functionality of the monomer is of prime importance. The number of bonding sites is referred to
as the functionality. (2 marks)
(c)
Polymer classification by chain identification
59
Homopolymers - consist of chains with identical bonding
linkages to each monomer unit. This usually implies that
the polymer is made from all identical monomer
molecules.
These may be represented as : -[A-A-A-A-A-A]-
Copolymers - consist of chains with two or more
linkages usually implying two or more different types
of monomer units.
These may be represented as : -[A-B-A-B-A-B]-
Polymers are further classified by the reaction mode of polymerization, these include:
Addition Polymers - the monomer molecules
bond to each other without the loss of any other
atoms. Alkene monomers are the biggest groups
of polymers in this class.
Condensation Polymers - usually two different monomer
combine with the loss of a small molecule, usually water.
Polyesters and polyamides (nylon) are in this class of
polymers.
Classification based upon the physical property related to heating:
Thermoplastics - plastics that soften when heated
and become firm again when cooled. This is the
more popular type of plastic because the heating
and cooling may be repeated.
Thermosets - plastics that soften when heated and can be
molded, but harden permanently. They will decompose
when reheated. An example is Bakelite, which is used in
toasters, handles for pots and pans, dishes, electrical outlets
and billiard balls.
(6 marks)
2 (a) Discuss the core characteristic concept of addition polymerization (12 marks)
(b) Compare condensation polymerization and addition polymerization. (4 marks)
(c) State the applications of condensation polymerization (4 marks)
Soln:
2(a)
Addition polymerization process proceeds in three stages namely initiation (birth), propagation
(growth) and termination (death). These are not distinct stages and all may be occurring at any
one time.
Initiation:
60
This stage involves the creation of the free-radical active center or labile group and usually takes
place in two steps:
- The formation of free radicals from the initiator and
- The creation of the active center. (2 marks)
The formation of free radicals from the initiator:
This is usually achieved using a catalyst (usually called initiator). Chemically these initiators are
capable of producing a free radical (•). (1 mark)
(1 mark)
When this split happens, two fragments result, each of which has one unpaired electron.
Molecules like this, with unpaired electrons are called free radicals. (1 mark)
Chain Propagation:
Propagation involves growth of the polymer chain by rapid sequential addition of monomer to
the active center. (1 marks)
As with the second step of initiation there are two possible modes of propagation (head to
head, head to tail) that can occur:
(2 marks)
Chain Termination:
In this stage, growth of the polymer chain is terminated. This can occur in a few different ways:
(1 mark)
• Bi-molecular coupling/combination
• Disproportionation
• Chain transfer (3 marks)
61
(b) Comparison
Addition polymerization Condensation polymerization
Has high molecular weight Has low molecular weight
There is no release of small molecules during
formation
Small molecules (like H2O, HCl etc)are
released during formation
Active sites are used up during reaction Active sites remain active throughout the
reaction
Occurs in three stages of initiator,
propagator and termination
Does not require initiator before reaction
commences
Are not bio-degradable Are bio-degradable
(5 marks)
(c)
This type of reaction is used for making important polymers like nylon, polyester
It is also the basis for the laboratory formation of silicates and polyphosphates
Nearly all biological transformations are condensation reactions e.g polypeptide synthesis
It is occasionally used to form simple hydrocarbons (4 marks)
62
COURSE CODE: CHM 432 COURSE TITLE: MINERAL PROCESSING
Write short notes on the under listed using equations where necessary.
1) Ore beneficiation
2) Primary melt
3) Primary geochemical dispersion
4) Name three aluminum containing ores, indicating their chemical
compositions.
5) Describe the procedure for obtaining aluminum from one of the ores named.
6) How would you catalogue minerals
7) What are the criteria required for a substance to be called a mineral?
8) Indicate with equation(s) the main stages involved in the production of
copper from its malte.
9) Explain with suitable chemical equations the processes involved in a blast
furnace during slag production.
What do understand by the terms
10) mineral saturation index
11) opaque minerals
12) solid solution
13) Using a tabular former, name ten minerals from Nigeria indicating
their state, location and their chemical compositions.
14) List the main classes of minerals.
63
COURSE CODE: CHM 439 COURSE TITLE: ANALYSIS OF SELECTED MATERIALS
Section 1
1. Differentiate between wet chemical analysis and spectroscopic chemical analysis of
minerals.
2. Write short notes on any five spectroscopic methods of analysis of minerals.
3. Identify the four types of Neutron Activation Analysis, stating their peculiarities.
Solutions to Section 1
1. (a) Wet chemical analysis involves the dissolution of a mineral in an acid and then analyzing
the solution while spectroscopic chemical analysis involves the use of energy source to
bombard a mineral in order to produce electromagnetic signals that can be detected and
analyzed.
2. The spectrometric methods include:
(i) Atomic Absorption Spectroscopy (AAS)
The atomic absorption spectrometer consists of a hollow cathode lamp, atomizer, a
monochromator, a detector, an amplifier and a recorder. AAS uses a controlled flame and
monochromator linked to a detector to search for wavelengths of light that are absorbed by
the flame.
(ii) Visible and Infrared Spectroscopy
This is the study of materials based on the light wavelengths. It can use ultraviolet light
generated by tungsten-halogen or deuterium light sources. Light beam is controlled and
split to measure air and the sample simultaneously. Visible light is very useful to study
the valence states of transition metals while infrared light studies are commonly applied to
H or C + O species. Using the known molar absorption coefficient of a particular species,
the Beer-Lambert law can be applied to calculate concentration of particular species.
(iii) Inductively Coupled Plasma (ICP) Spectrometry uses a gas (typically argon) to
64
move the sample vapour into a chamber under high vacuum where the sample and gas are
heated such that elements will give off a characteristic wavelength of light.
(iv) X-ray Fluorescence (XRF) is a technique that has broad application as multiple
elements/oxides can be analyzed simultaneously. In this technique, high voltage accelerates
electrons towards a metal target to produce a specific fixed wavelength x-ray beam that hits
the sample. Inner shell electrons in the sample are ejected and photons are emitted as outer
shell electrons drop to inner orbitals. Photons have characteristic energies and elemental
concentrations can be calculated with this technique by comparing sample intensities to a
known standard.
(v) X-ray Diffractometry (XRD) is a technique that is only appropriately applied to pure
amorphous or crystalline substances and allows users to learn about the structure of the
compound. An x-ray beam is fired at a sample over a series of angles but keeping the source
and target (sample) always at the same distance. The reflected or diffracted x-rays provide a 2-
theta angle such that Bragg’s Law can be solved.
(vi) Electron Probe Microanalysis (EPMA)
In EPMA, a beam of electrons is generated and sent from the electron gun through a series of
lenses and apertures towards the target. The diameter and strength of the beam can be modified
based on the current and accelerating voltage used to generate the beam. The electrons in the
specimen are excited and then, as electrons relax and fall back from an excited to a ground
state they will fluoresce and generate x-rays. X-rays generated from the beam-specimen
interaction are characterized by energy and wavelength to identify the element, intensity is
used to analyze concentration. Samples must then be carbon coated and kept under vacuum
before analysis. Samples do not have to be powered or dissolved and the analysis is non-
destructive.
(vii) Scanning Electron Microscopy (SEM)
This is similar to EPMA in that an electron gun is used to generate and fire electrons in a beam
at a sample. SEM can produce incredible images using both secondary electron scatter or
65
backscattered electrons. SEM can be performed on thin sections, angular mineral grains as well
as carbon based materials. Samples do not have to be powered or dissolved and the analysis is
non-destructive.
(viii) Mass Spectrometry
Mass spectrometric analysis comes in a variety of forms. Some common types of mass
spectrometry are secondary ion mass spectrometry (SIMS), thermal ionization mass
spectrometry (TIMS) and multicollector mass spectrometry. All of these techniques are similar
in that an ion beam is generated by a type of plasmatron or an alkali metal. The beam is then
focused at a sample and used to erode and sputter the target area. This sputtered and ionized
material is then carried into the spectrometer by a counter gas.
(ix) Photon –Induced Emission Spectroscopy
There are two types of photon-induced spectroscopy: gamma-ray and x-ray hence photon –
induced (gamma) emission (PIGE) spectroscopy and photon–induced x-ray emission (PIXE)
spectroscopy. These techniques use a proton beam at very high energy to produce incredibly
small, electro-magnetically focused beams with little to no background interference signal.
(x) Raham Spectroscopy
This is a good technique to use to identify minerals (even if the grain size is very small or the
crystal shape is totally anhedral). This technique takes advantage of a fundamental interaction
of a photon beam and a target. Photons can be scattered back off of a target either elastically
(Rayleigh scattering) or in-elastically (Raman scattering). Inelastic scattered photons typically
have a longer wavelength than elastically scattered photons. The difference in wavelengths is
called the Raman shift and is characteristic of specific mineral phases.
(xi) Neutron Activation Analysis
All types of neutron analysis are based on the idea that any element can be made radioactive if
it is bombarded with enough energy. In this type of spectroscopy, samples are placed in a
nuclear reactor where they are targeted by neutrons to generate a thermal flux. Known
standards are placed in the reactor along with the unknown. Both the sample and the unknown
66
are removed from the reactor together. Immediately, both materials begin to decay and produce
gamma radiation that can be counted and used as a proxy for concentration.
(xii) Mossbauer Spectroscopy
This technique is good for understanding the valence state of Fe that is usually related to the
amount of water available when a rock is crystallizing. It relies on the study of gamma-ray
particles generated when a nucleus recoils after emitting energy.
3. Types of Neutron Activation Analysis
(i) Prompt Gamma-Ray Neutron Activation Analysis (PGNAA)
Radioactive nuclides are counted in the reactor as the sample is irradiated. This is
useful for elements that have very short half-lives.
(ii) Delayed Gamma-Ray Neutron Activation Analysis (DGNAA)
Radioactive nuclides are counted once the sample and a standard is removed from the
reactor over a period of days. This is the most useful as small volumes of sample can be
used to study 25 to 30 elements in a single run.
(iii) Radiochemical Neutron Activation Analysis (RNAA)
This is an almost identical technique to DGNAA but one has to physically separate
phases after they are irradiated. This is difficult and expensive and not common.
(iv) Fast Neutron Activation Analysis (FNAA). This technique is similar to PGNAA in that
nuclides are counted soon after irradiation, but in this case they are based through a
flux source and counter tube.
Section 2
1 (a) What is a soil? (2½ marks)
(b) Briefly state the reasons why the need of a soil tests? (3 marks)
(c) When is it advisable for soil sampling? (9 marks)
67
(d) Highlight the parameters required in basic soil analysis (5 marks)
(e) How do you manage an alkaline soil? (4 marks)
Soln:
1(a) What is a soil? (2½ marks)
The soil is a key component of terrestrial ecosystems, both natural and agricultural, being
essential for the growth of plants and the degradation and recycling of dead biomass. It is a
complex heterogeneous medium comprising mineral and organic solids, aqueous and gaseous
components.
(b) Briefly state the reasons why the need of a soil tests? (3 marks)
• Encourages plant growth by providing the best lime and fertilizer recommendations • Diagnoses whether there is too little or too much of a nutrient. • Promotes environmental quality. • Saves money that might otherwise be spent on unneeded lime and fertilizer.
(c) When is it advisable for soil sampling? (9 marks)
• Soil samples may be collected at any time of the year, provided that the area is not suffering from prolonged drought, that no nitrogen has been applied in the last 30 days and no sulfur has been used in the last six months.
• Late spring and early summer sampling, shows the soil's fertility at its best. • However, if no samples have been taken within the last two years, the best time to sample is as
soon as circumstances permit. • Generally, sampling should be done every year if fertility is high and / or trace elements are being
used to achieve top yields. • CAUTION: no soil samples should ever be sent for analysis when a soil is so extremely dry that
plants will not grow there.
(d) Highlight the parameters required in basic soil analysis (5 marks)
• Total Exchange Capacity (T.E.C.) • Soil pH • Organic Matter (Humus) as percent • Nitrogen (N released from colloidal humus) • Sulfate (Expressed as elemental sulfur) in ppm • Phosphates (as P205) • Trace elements: Boron, Iron, Manganese, Copper and Zinc, in ppm. • Cobalt, Molybdenum, Chlorides, in ppm • Aluminum & Limestone Analysis
68
• Manure Analysis (includes S, Ca and Mg, plus B, Fe, Mn, Cu, & Zn)
(e) How do you manage an alkaline soil? (4 marks)
• Soils with moderate to high alkalinity (pH above 7.5) can be managed by increasing the organic matter, using organic mulches, and light frequent irrigation. Soils with a pH above 7.3 and/or with free lime cannot be adequately amended for acid-loving plants.
• In near-neutral pH soils rich with organic matter and without free-lime, gardeners may find a slight decrease in soil pH over many decades. This occurs as irrigation leaches out some naturally occurring elements (calcium and magnesium) contributing to the higher pH.
2 Write short notes on the following:
(i) Soil pH (4 marks) (ii) Buffer Index (4 marks)
(iii) Soil test (4 marks) (iv) Soil organic matter (7½ marks)
(v) oxidation and reduction in soil (4 marks)
Soln:
2 Write short notes on the following:
(i) Soil pH
• Soil pH is a measurement of the acidity or alkalinity of a soil. • On the pH scale, 7.0 is neutral. Below 7.0 acid, and above 7.0 is basic or alkaline. A pH range of
6.8 to 7.2 is termed near neutral. • Areas of the world with limited rainfall typically have alkaline soils while areas with higher rainfall
typically have acid soils. • The pH of a soil applies to the H+ ion concentrate in the solution present in soil pores which is in
dynamic equilibrium with the predominantly –ve charged surfaces of the soil particles. Hydrogen ions are strongly attracted to the surface –ve charges, and they have the power to replace most other cations.
• Soil pH is an important chemical property because it affects the availability of nutrients to plants and the activity of soil microorganisms. The influence of pH on nutrient availability as indicated in Iron chlorosis is due to alkaline soil pH. (4 marks)
(ii) Buffer Index
• A laboratory test called buffer index measures the responsiveness of the soil to lime applications. The soil test will give recommendations on application rates based on the buffer index rather than just the pH. Lime is commonly sold as ground agricultural limestone. It varies in how fine it has been ground. The finer the grind, the more rapidly it becomes effective in lowering pH. Calcitic lime mostly contains calcium carbonate (CaC03).
69
• Dolomitic lime contains both calcium carbonate and dolomite [MgCa(CO3)2]. On most soils, both are generally satisfactory. However, on sandy soils low in organic matter, dolomitic lime may supplement low magnesium levels. (4 marks)
(iii) Soil test
• A soil test is a process by which elements (phosphorus, potassium, calcium, magnesium, sodium, sulfur, manganese, copper and zinc) are chemically removed from the soil and measured for their "plant available" content within the sample.
• The quantity of available nutrients in the sample determines the amount of fertilizer that is recommended.
• A soil test also measures soil pH, humic matter and exchangeable acidity. These analyses indicate whether lime is needed and, if so, how much to apply. (4 marks)
(iv) Soil organic matter
• The main feature which distinguishes soil from regolith (decomposed rock) is the presence of living organisms, organic debris and humus. All soils contain organic matter, although the amount and type may considerably.
• Colloidal soil organic matter has a major influence on the chemical properties of soils and can be divided into “non-humic” and “humic” substances. The non-humic substances comprise unaltered biochemicals such as amino acids, carbohydrates, organic acids, fats and waxes that have not changed from the form in which they were synthesized by living organisms.
• Humic substances are a series of acidic, yellow to black coloured polyelectrolytes of moderately high molecular weight. They are formed by secondary synthesis reactions involving microorganisms and have characteristics which are dissimilar to any compounds in living organisms.
• Humic substances are a series of acidic, yellow to black coloured polyelectrolytes of moderately high molecular weight. They are formed by secondary synthesis reactions involving microorganisms and have characteristics which are dissimilar to any compounds in living organisms. Traditionally, humus has been separated in the laboratory into three fractions:
• Humic, which is insoluble in alkali • Humic acid, which is soluble in alkali and insoluble in acid • Fulvic acid, which is soluble in both acid and alkali • These substances cannot be regarded as distinctly different, but merely as part of a continuum of
compounds varying in molecular weight C content, O content, acidity and cation exchange capacity in the order. Humic > humic acid > fulvic acid with N content decreasing through the same sequence.
• Methods used to determine the organic matter content of soils include either the percentage loss in weight after ignition in a furnace at 375oC for 16 hr or the oxidation of C by acid dichromate followed by the titration of excess dichromate. Organic matter contains about 58-60% organic C.
• (% org C x 1.67 = %OM). • Within the soil profile, the organic matter content is always highest in the surface horizon, but
podzols may have some translocated humic material lower down the profile. (7½ marks)
70
(v) oxidation and reduction in soil
• Soils are subject to variations in oxidation reduction status and this mainly affects the elements C,N,O,S, Fe and Mn, although Ag, As, Cr, Cu, Hg and Pl can be affected.
• Redox equilibria are controlled by the aqueous free-elections activity, which can be expressed as either the pE value (the -ve log of the election activity) or Eh (the millivolt difference in potential between a Pt electrode and the standard H electrode).
• The pE unit has the advantage of allowing electrons to be treated like other reactants or products, allowing both chemical and electrochemical equilibria to be expressed with the single equilibrium constant.
• The conversion factor for the units is Eh (mV) =59.2pE. Large positive values of pE (or Eh) favour the existence of oxidized species, and low or negative values of pE (or Eh) are associated with reduced species. (4 marks)