Web viewCompare and contrast nuclear radiations( α, β-, β+, γ) emitted from...

Grade 12ES Subject Chemistry

Chapter 24. Nuclear Chemistry

Sections 24.1

Learning Outcomes

1. Distinguish between the electrostatic forces (between protons) and the nuclear forces (between neutrons and protons) inside the nucleus

2. Explain why large nuclei are radioactive3. Define radioactivity 4. Relate large and small nuclei stability with respect to the

ratio of neutrons to protons5. Compare between the atomic number (Z)and mass

number(A) of a nucleus6. Define isotopes and its notation XZA

7. Compare and contrast nuclear radiations( α, β-, β+, γ) emitted from unstable nuclei in terms of nature, symbol, mass, charge, penetration power

8. Write nuclear equations to predict the mass number and the atomic number of a daughter nucleus when a parent nucleus emits alpha, beta, or gamma radiations

9. Define half- life of a radioactive isotope10.Calculate the remaining amount of radioactive element using thr following mathematical formula

N = N (12 )n

Raseena Sajjad ATHS/ FUJ

Chemistry question bank

Multiple Choice Questions1. A lightweight isotope is likely to be stable if the ratio of protons to neutrons in its nucleus is(Outcome 4)

A 1:2.

B 1:1.

C 2:1

D 5:1

2. The only nucleon among the following is the(Outcome 1)A Positron

B Neutron

C electron

D Beta particle

3. The isotope formed by the beta decay of 4019K has an atomic number of(Outcome 6)

A 18

B 39

C 20

D 21


4. The positron produced during positron emission comes from a(n) (Outcome 7)

A neutron.

B proton

C electron

D positron

6. The decay of 162 Tm 69 yields 68Er162 and (Outcome 8)

A 2 He4

B -e

C +e

D

8. The most penetrating form of nuclear radiation is(Outcome 7)

A alpha rays

B beta rays

C gamma rays

D positrons.


9. In an atom, the strong nuclear force acts on(Outcome 1)

A protons only

B neutrons only

C protons and neutrons

D protons, neutrons, and electrons

10. The half-life of calcium-47 is about 5 days. Starting with 64 g of this isotope, what would be the amount remaining after 20 days? (Outcome 10)

A 32 g

B 16g

C 8g

D 4g

11. A nuclear reaction may involve: (Outcome 1)

A protons

B neutrons

C electrons

D Protons& neutrons

12. Unstable nuclei can break apart spontaneously, changing the identity of the _____ . (Outcome 3)


A elements

B atoms

C compounds

D reactions

15. Alpha particles have a _____ charge. (Outcome 7)

A -1

B 0

C +1

D +2

16. How does the nucleus of an atom change after a gamma irradiation? (Outcome 8)

A The atomic mass reduces by four and the atomic number reduces by two.

B The atomic mass remains the same, but the atomic number increases by one.

C The atomic mass remains the same, but energy is lost as the nucleus decays.

D The atomic mass changes by one, but the atomic number remains the same.

17. What is the reason for the decay of naturally radioactive elements? (Outcome 8)

A To reduce the number of neutrons as the elements lie above the band of stability.


B To reduce the number of protons as the elements lie below the band of stability.

C To reduce the number of either neutrons or protons to lie in the band of stability.

D To release the energy from nucleus in the form of gamma radiation.

18. Compared to an electron, a positron has (Outcome 7)

A the same mass and chargeB the same chargeC different mass and chargeD the same mass, but a different charge

19. Identify the type of radiation that is produced when a neutron is converted to a proton. (Outcome 7)

A Alpha

B Beta

C Gamma

D Positron

21. Atoms with the same atomic number but different mass numbers are

(Outcome 6)

A isomers


B allotropes

C isotopes

D Isobars

Problems 1.Iron 59, a radioactive isotope, has a half life of 46 days. Calculate the time

by which 30.0 micrograms falls to 14% of the initial value in the body of a cancer patient. (Outcome 10)

ANS ; 131 days

2. Calculate the remaining amount of 100.0 grams of cobalt-60 after 1600 years. The half life of cobalt-60 is 5272 years. (Outcome 10)

ANS ; 81.03 grams

3. 160.0 grams of radium 226 is reduced to 114.6 grams in 782 years. What is the half life of the compound? (Outcome 10)ANS: 1620 years

4. Examine the figure provided and approximate the number of years in one half life of strontium. (Outcome 9&10)


ANS: Aprox 25 yrs

5. Explain the following equation. (Outcome 10)

ANS:N = remaining amount of radioactive elementNo = initial amount of elementn = number of half lives that have passed. 6. An 80.0-g sample of a radioactive compound, radium-226, is reduced to 57.3 g in 782 years. What is the half-life of the compound? (Outcome 10)

ANS;, half-life 1620 years

8. Krypton-85 is used in indicator lights of appliances. The half-life of krypton-85 is 11 y. How much of a 2.000-mg sample remains after 33 y?(Outcome 10)

ANS; 0.25 mg

9. The half-life of polonium-218 is 3.0 min. If you start with 20.0 g, how long will it be before only 1.0 g remains? (Outcome 10)

Ans;13 min.


10. Technetium-99m is widely used in diagnosing medical problems. The graph below shows the rate at which a 200-gram sample of technetium-99m decays. Answer the following questions using the graph. (Outcome 9&10)

1. What is the half-life of technetium-99m?

The half-life is approximately 6 hr.

2.Estimate the amount of the original sample of technetium-99m that remain

a. after 1 h; 180g c. after 10 h; 70g

b. after 5 h; 120 g d. after 1 day. 12 g


3. Suppose that a doctor needs 25 g of technetium-99m in a medical procedure, and a sample of 100 g is made at 8:00 A.M. What is the latest time at which the procedure can be carried out? Why?

The latest time would be at roughly 8 P.M. the same day. Two half-lives, 6 hr. each, would have elapsed.

4. The technetium-99m is considered to be no longer useable when less than 6 g remains. At what time would the sample described in the preceding question become unusable?The sample would become unusable at roughly 8 A.M. the next day.

5. Radioactive isotopes used for medical purposes are usually produced in anuclear laboratory and shipped to hospitals. What problem can you see inproducing and using technetium-99m by this system?

The isotope may have decayed during shipping.

6. Technetium-99m decays in two steps, emitting first a gamma ray, then a beta particle.

Answer the Following Questions

1. Explain why the neutron-to-proton ratio of stable nuclei increases as the atomic number increases (Outcome 4)

As atomic number increases, more and more neutrons are needed to produce a strong nuclear force that is sufficient to balance the electrostatic repulsion between protons.


2. Compare and contrast chemical reactions and nuclear reactions in terms of energy changes and the particles involved. (Outcome 1)

Nuclear reactions release more energyper mole. Nuclear reactions involve neutronsand protons, whereas chemical reactions involve electrons.

3. Define the band of stability and relate it to the value of the neutron-to-proton ratio. (Outcome 4)

The band of stability is the area on a graph showing the number of neutrons versus the number of protons that contains all the stable nuclei. It corresponds to a neutron-toproton ratio of 1:1 to 1.5:1 depending on the atomic number.

4. Explain why radioisotopes above the band of stability are unstable. (Outcome 4)They are unstable because they have too many neutrons relative to their number of protons.

7. Define the term half-life. (Outcome 9)

A half-life is the time required for one-half of a radioisotope’s nuclei to decay into its products.

8. TheFigure shows alpha particles, beta particles, and gamma rays passing through a screen and between two charged plates. What can you infer about the identity of a, b, and c? Explain your answer. (Outcome 7)


A must be beta particles because their negative charge would cause them to be deflected away from the negatively charged plate. B must be gamma rays because they have no charge and would not be deflected by the charged plates. C must be alpha particles because their positive charge would cause them to be deflected away from the positively charged plate.

9. In which region(s) in Figure are you likely to find (Outcome 4)a. stable nuclei?b. nuclei that undergo alpha decay?c. nuclei that undergo beta decay?d. nuclei that undergo positron emission?

10.Define Radioactivity. (Outcome 3)

The spontaneous emission of radiation by an unstable atomic nucleus is called Radio activity.

13.Complete the following nuclear equations. (Outcome 8)

a)


11 11C → B +

6 5

b)

238 4U → ----- + He

92 2

c)

14 14C → N +

6 7

d)

226 4

Ra → + He88 2


e)

15 15

O → N +8 7


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