CHE 107 Spring 2018 Exam 1

Your Name: Your ID:

Question #: 1

A.

B.

C.

D.

Fill in the blanks with the letter that would represent the electron density for A sigma (σ) bonding molecular orbital 1 A pi antibonding (∏*) molecular orbital 2

1.

2.

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Question #: 2

Using the empty MO diagram below, we can predict that C22– will contain a _____ bond and be _____.

A. double; paramagnetic

B. triple; diamagnetic

C. double; diamagnetic

D. triple; paramagnetic

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Question #: 3

Which statement is false?

A. Molecular orbitals result from linear combinations of atomic orbitals.

B. Combinations of antibonding molecular orbitals produce a conduction band.

C. Bonding molecular orbitals are higher in energy than the atomic orbitals combined to

form them.

D. Antibonding molecular orbitals are less stable than the atomic orbitals combined to form

them.

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Question #: 4

Use the diagram to answer the following questions.

Which one is an insulator? 1 [A, B, or C] Which one is a semi-conductor? 2 [A, B, or C] Which diagram best represents germanium? 3 [A, B, or C}

1.

2.

3.

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Question #: 5

To prepare a p-type semiconductor a crystal of 1 [arsenic, boron, silicon] is doped with a trace amount of 2 [arsenic, boron, antimony].

1.

2.

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Question #: 6

The picture of a(n) 1 [amorphous, crystalline] solid below has a 2 of six.

1.

2.

Item Weight: 1.0

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Question #: 7

Copper crystallizes as a face-centered cubic unit cell containing 1 atom(s) per unit cell, which has a 2 [lower, higher] packing efficiency than polonium, a simple cubic unit cell containing 3 atom(s) per unit cell.

1.

2.

3.

Question #: 8

State the fraction of each colored atom and determine the total number of each atom designated in the unit cells below. For all three unit cells, the fraction of each black atom (corner) within the cell is 1 . In the middle unit cell, the fraction of the blue atom (body) within the cell is 2 . For the unit cell on the right, the fraction of each green atom (face) within the cell is 3 .

1.

2.

3.

Item Weight: 1.0

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Question #: 9

At low temperature, the noble gas argon crystallizes in a face-centered cubic (fcc) crystal structure with an edge length of 544 pm. What is the density of the argon crystal?

1 g/cm3 Report your answer with three significant figures. Do NOT include units with your answer.

1.

____________________________________________________________________________

Question #: 10

Which element crystallizes in a simple cubic structure with a density of 9.32 g/cm3 and an edge length of 334 pm?

A. polonium (Po)

B. platinum (Pt)

C. thorium (Th)

D. iodine (I)

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Question #: 11

An oxide of copper crystallizes in a cubic unit cell with oxide ions (red) on all corners and body position, and copper ions (gray) in body positions. What is the empirical formula of the oxide?

A. Cu4O9

B. Cu2O

C. Cu4O5

D. Cu2O3

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Question #: 12

A chemistry student examines an unidentified metal sample weighing 20.0 grams. She determines that it transfers 1200 J of energy to heat a water sample. During this experiment the

metal cools from an initial temperature of 70.0 ºC to 30.0 ºC.

Which statement is true about the metal sample?

A. The metal has a heat capacity of 30.0 J/ºC and a specific heat of 30.0 J/g·ºC.

B. The metal has a heat capacity of 60 J/ºC and a specific heat of 3.00 J/g·ºC.

C. The metal has a heat capacity of 30.0 J/ºC and a specific heat of 1.50 J/g·ºC.

D. The metal has a heat capacity of 3.00 J/ºC and a specific heat of 60.0 J/g·ºC.

____________________________________________________________________________

Question #: 13

A 75.0 g block of aluminum, initially at 90.0 ºC, releases 4036 J of heat as it cools. What is the final temperature of the aluminum block? The specific heat of aluminum is 0.897 J/g·ºC. 1 ºC Report your answer with three significant figures. Do NOT include units with your answer.

1.

____________________________________________________________________________

Question #: 14

A 10.0 g metallic sample releases 171 J of heat as it cools from 65.5 ºC to 21.1 ºC. What is the identity of the metal?

Sample Cs(J/g·ºC)

aluminum 0.902

iron 0.450

copper 0.385 gold 0.129

A. aluminum

B. iron

C. copper

D. gold

Question #: 15

A 2.74 g sample of a metal is warmed to 72.1 ºC and submerged in 15.2 g of water initially at 24.7 ºC. The final temperature of the mixture is 26.3 ºC. What is the specific heat capacity of the unknown metal? 1 J/g·ºC

Specific heat capacity of water = 4.184 J/g·ºC

Enter your answer with two significant figures. Do NOT include units in your answer.

1.

____________________________________________________________________________

Question #: 16

Given the standard enthalpy of combustion of cyclohexane, C6H12(l) (MW 84.16 g/mol), where the reaction is given by: C6H12(l) + 9 O2(g) → 6 CO2(g) + 6 H2O(l) ΔH°rxn = –3919.4 kJ/mol How much heat (in kJ) is released when 10.0 mL of cyclohexane (density = 0.779 g/mL) is combusted?

A. 7.79 kJ

B. 3.92 × 103 kJ

C. 363 kJ

D. 598 kJ

___________________________________________________________________________

Question #: 17

Fill in the blanks with the physical state(s) (solid, liquid, gas) that exist at the listed temperatures. If more than one state would be present, put in both states separated by a comma. 140°C 1 70°C 2 100°C 3

1.

2.

3.

Question #: 18

How much energy is required to convert 23.0 g (0.250 mol) of solid toluene, C7H8(s), at –95°C, to gaseous toluene, C7H8(g), at 111°C?

melting point –95°C

boiling point 111°C

ΔHfus 6.64 kJ/mol

ΔHvap 38.1 kJ/mol

Cs of C7H8(l) 1.69 J/g·°C

Cs of C7H8(g) 1.12 J/g·°C

A. 11.2 kJ

B. 6.81 kJ

C. 9.26 kJ

D. 19.2 kJ

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Question #: 19

A 15.0 g iron nail at 85.0 °C is placed in 50.0 mL of water at 21.0 °C. What is the final temperature of both substances upon reaching thermal equilibrium? 1 ºC The density of water is 1.00 g/mL. The specific heat capacity of iron is 0.450 J/g·°C. The specific heat capacity of water is 4.184 J/g·°C. Report your answer with TWO significant figures. Do NOT include units in your answer.

1.

____________________________________________________________________________

Question #: 20

A certain process releases 165 kJ of energy as heat and does 215 kJ of work on the surroundings. What is the change in internal energy of the system? 1 kJ Report your answer with three significant figures. Include the sign. Do NOT include units in your answer.

1.

Question #: 21

A sample of gas occupies a volume of 750. mL. As it expands at a constant pressure of 755 torr, it does 80.5 J of work on its surroundings. What is the final volume, in mL, of the gas? (1.00 L.atm = 101.3 J) Hint: Note the units of each quantity. 1 mL Report your answer with four significant figures. Do NOT include units with your answer. Use the format 2.222E2 or 2.222E-2 for answers in scientific notation.

1.

____________________________________________________________________________

Question #: 22

A solid, X, has a molar mass of 72.1 g/mol. In a constant-pressure calorimeter, 22.4 g of X is dissolved in water at 20.0 °C. The mass of the solution is 296 grams. X(s) → X(aq) The temperature of the resulting solution rises to 27.9 °C. Assuming the solution has the same specific heat as water (4.184 J/g °C) and there is negligible heat lost to the surroundings, what is ΔHrxn?

A. 32 kJ/mol

B. –32 kJ/mol

C. 24 kJ/mol

D. –24 kJ/mol

____________________________________________________________________________

Question #: 23

Coal gasification converts coal into a combustible mixture of carbon monoxide and hydrogen, called coal

gas, in a gasifier by the following reaction:

C(s) + H2O(l) → CO(g) + H2(g)

What is Hrxn , given:

2 C(s) + O2(g) → 2 CO(g) Hrxn = −222 kJ

2 H2(g) + O2(g) → 2H2O(g) Hrxn = −484 kJ

H2O(l) → H2O(g) Hrxn = 44 kJ

A. 175 kJ

B. –309 kJ

C. –662 kJ

D. 131 kJ

Question #: 24

Calculate ΔHrxn for the reaction: CH4(g) + 4 Cl2(g) → CCl4(g) + 4 HCl(g) Using the following reactions and given ΔH's: C(s) + 2 H2(g) → CH4(g) ΔH = –74.6 kJ C(s) + 2 Cl2(g) → CCl4(g) ΔH = –95.7 kJ H2(g) + Cl2(g) → 2 HCl(g) ΔH = –92.3 kJ ΔHrxn = 1 kJ

1.

____________________________________________________________________________

Question #: 25

Which chemical equation has ΔHrxno that is equal to the ΔHfo of the product?

A. C3H6(g) + 9/2 O2(g) →3 CO2(g) + 3 H2O(l)

B. Na(s) + 1/2 I2(s) →NaI(s)

C. H2(g) + Cl2(g) →2 HCl(g)

D. H2O(l) →H2(g) + 1/2 O2(g)

____________________________________________________________________________

Question #: 26

Given the information below, what is ΔHf° for SF6(g)? 2 CoF3(g) + SF4(g) → SF6(g) + 2 CoF2(g) ΔHrxn° = 376 kJ/mol

Compound ΔHf° (kJ/mol)

CoF3(g) –790

SF4(g) –728

SF6(g) ?

CoF2(g) –356

A. –905 kJ/mol

B. –638 kJ/mol

C. –1220 kJ/mol

D. 2260 kJ/mol

Question #: 27

Calculate the lattice enthalpy, ΔHlattice, of silver chloride, AgCl, using the Born-Haber cycle and the information given below.

Ag(s) + 1/2 Cl2(g) → AgCl(s)

ΔHf° AgCl(s) –127 kJ/mol

Enthalpy of sublimation, ΔHs° Ag(s) 284 kJ/mol

1st ionization energy (IE) of Ag(g) 731 kJ/mol

1st electron affinity (EA) of Cl(g) –349 kJ/mol

Bond dissociation energy (BE) of Cl2(g) 244 kJ/mol

A. 854 kJ/mol

B. 783 kJ/mol

C. 915 kJ/mol

D. 661 kJ/mol

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Question #: 28

Use bond enthalpies to determine the ΔHrxn for this reaction: N2(g) + 3H2(g) → 2NH3(g). Scroll down to see all of the information. Report your answer with three significant figures. Do NOT include units in your answer.

Bond Energies

Bond Energy (kJ/mol)

H–H 436

H–N 390

N–N 240 N≡N 941

ΔHrxn = 1 kJ/mol

1.

Question #: 29

Entropy is a state function that _____ depend on the path taken between the final and initial states. Entropy is defined as the ratio of heat, qrev, divided by the _____ temperature.

A. does; Celsius

B. does; Kelvin

C. does not; Celsius

D. does not; Kelvin

____________________________________________________________________________

Question #: 30

Water (1000 g) at 50ºC is placed in a metal pan (800 g) at 25ºC. Which statement regarding the spontaneous heat transfer is correct?

A. Heat will be transferred from the metal to the water, so the final temperature of the water

will be higher than the final temperature of the metal.

B. Heat will be transferred from the water to the metal, so the final temperature of the metal

will be higher than the final temperature of the water.

C. Heat will be transferred from the metal to the water, so the final temperature of the water

will be equal to the final temperature of the metal.

D. Heat will be transferred from the water to the metal, so the final temperature of the metal

will be equal to the final temperature of the water.

DRAFTDo Not Use Until Posted.

CHE 107 Spring 2018 Exam 1 - Confidential

Your Name: Your ID:

attachment_for_pubExamUID_lnxp115180241575327246XX_248.jpg

Question #: 1

A. 

 

B. 

   

         

C.    D.     

    

 Fill in the blanks with the letter that would represent the electron density for 

A sigma (σ) bonding molecular orbital     1    

A pi antibonding (∏*) molecular orbital     2    

1. D

2. A

Question #: 2

Using the empty MO diagram below, we can predict that C22– will contain a _____ bond and

be _____.

A. double; paramagnetic

✓B. triple; diamagnetic C. double; diamagnetic D. triple; paramagnetic

Question #: 3

Which statement is false?

A. Molecular orbitals result from linear combinations of atomic orbitals. B. Combinations of antibonding molecular orbitals produce a conduction band.

✓C. Bonding molecular orbitals are higher in energy than the atomic orbitals combined toform them.

D. Antibonding molecular orbitals are less stable than the atomic orbitals combined to formthem.

Question #: 4

Use the diagram to answer the following questions.

Which one is an insulator?     1      [A, B, or C]

Which one is a semi-conductor?     2     [A, B, or C]

Which diagram best represents germanium?     3     [A, B, or C}

 

 

1. C|C.|

2. B|B.|

3. B|B.|

Question #: 5

To prepare a p-type semiconductor a crystal of     1     [arsenic, boron, silicon] is doped with a

trace amount of      2     [arsenic, boron, antimony].

1. silicon

2. boron

Question #: 6

The picture of a(n)     1     [amorphous, crystalline] solid below has a     2     of six.

1. crystalline

2. coordination number

Question #: 7

Copper crystallizes as a face-centered cubic unit cell containing     1     atom(s) per unit cell,

which has a     2     [lower, higher] packing efficiency than polonium, a simple cubic unit cell

containing     3     atom(s) per unit cell.

1. 4

2. higher

3. 1

Question #: 8

State the fraction of each colored atom and determine the total number of each atom designated

in the unit cells below.

For all three unit cells, the fraction of each black atom (corner) within the cell is     1    .

In the middle unit cell, the fraction of the blue atom (body) within the cell is     2    .

For the unit cell on the right, the fraction of each green atom (face) within the cell is     3    .

1. 1/8|0.125|.125|eigth|one-eighth|

2. 1|1.|one|

3. 1/2|0.5|.5|half|

Question #: 9

At low temperature, the noble gas argon crystallizes in a face-centered cubic (fcc) crystal

structure with an edge length of 544 pm. What is the density of the argon crystal?

    1     g/cm3

Report your answer with three significant figures. Do NOT include units with your answer.

1. 1.65

Question #: 10

Which element crystallizes in a simple cubic structure with a density of 9.32 g/cm3 and an edge

length of 334 pm?

✓A. polonium (Po)

B. platinum (Pt) C. thorium (Th) D. iodine (I)

Question #: 11

An oxide of copper crystallizes in a cubic unit cell with oxide ions (red) on all corners and body

position, and copper ions (gray) in body positions.  What is the empirical formula of the oxide?

 

A. Cu4O9

✓B. Cu2O C. Cu4O5 D. Cu2O3

Question #: 12

A chemistry student examines an unidentified metal sample weighing 20.0 grams. She

determines that it transfers 1200 J of energy to heat a water sample. During this experiment the

metal cools from an initial temperature of 70.0 ºC to 30.0 ºC.

Which statement is true about the metal sample?

A. The metal has a heat capacity of 30.0 J/°C and a specific heat of 30.0 J/g·°C. B. The metal has a heat capacity of 60 J/°C and a specific heat of 3.00

J/g·°C. ✓C. The metal has a heat capacity of 30.0 J/ºC and a specific heat of

1.50 J/g·°C. D. The metal has a heat capacity of 3.00 J/ºC and a specific heat of

60.0 J/g·°C.

Question #: 13

A 75.0 g block of aluminum, initially at 90.0 ºC, releases 4036 J of heat as it cools. What is the

final temperature of the aluminum block? The specific heat of aluminum is 0.897 J/g·ºC.

    1     ºC

Report your answer with three significant figures. Do NOT include units with your answer. 

1. 30.0

Question #: 14

A 10.0 g metallic sample releases 171 J of heat as it cools from 65.5 ºC to 21.1 ºC. What is the

identity of the metal?

 

A. aluminum B. iron

✓C. copper D. gold

Question #: 15

A 2.74 g sample of a metal is warmed to 72.1 ºC and submerged in 15.2 g of water initially at

24.7 ºC.  The final temperature of the mixture is 26.3 ºC.  What is the specific heat capacity of

the unknown metal?

    1     J/g·ºC

Specific heat capacity of water = 4.184 J/g·ºC

Enter your answer with TWO significant figures.  Do NOT include units in your answer.

1. 0.81

Sample Cs(J/g·ºC)

aluminum 0.902

iron 0.450

copper 0.385

gold 0.129

Question #: 16

Given the standard enthalpy of combustion of cyclohexane, C6H12(l) (MW 84.16 g/mol), wherethe reaction is given by: C6H12(l) + 9 O2(g) → 6 CO2(g) + 6 H2O(l)    ΔH°rxn = –3919.4 kJ/mol How much heat (in kJ) is released when 10.0 mL of cyclohexane (density = 0.779 g/mL) iscombusted?

 

A. 7.79 kJ B. 3.92 × 103 kJ 

✓C. 363 kJ D. 598 kJ

Question #: 17

Fill in the blanks with the physical state(s) (solid, liquid, or gas) that exist at the listed

temperatures. If more than one state would be present, put in both states separated by a comma.

You may need to scroll down to see all.

140°C     1    

70°C     2    

100°C     3    

1. gas

2. solid,liquid|solid, liquid|liquid,solid|liquid, solid|

3. liquid

Question #: 18

How much energy is required to convert 23.0 g (0.250 mol) of solid toluene, C7H8(s), at –95°C,

to gaseous toluene, C7H

8(g), at 111°C?

 

 

A. 11.2 kJ B. 6.81 kJ C. 9.26 kJ

✓D. 19.2 kJ

Question #: 19

A 15.0 g iron nail at 85.0 °C is placed in 50.0 mL of water at 21.0 °C.  What is the final

temperature of both substances upon reaching thermal equilibrium?

    1     ºC

The density of water is 1.00 g/mL.

The specific heat capacity of iron is 0.450 J/g·°C.

The specific heat capacity of water is 4.184 J/g·°C. 

 

Report your answer with TWO significant figures. Do NOT include units in your answer.

 

1. 23

melting point –95°C

boiling point 111°C

Hfus 6.64 kJ/mol

Hvap 38.1 kJ/mol

Cs of C7H8(l) 1.69 J/g·°C

Cs of C7H8(g) 1.12 J/g·°C

Question #: 20

A certain process releases 165 kJ of energy as heat and does 215 kJ of work on the surroundings.

What is the change in internal energy of the system?

    1     kJ

Report your answer with three significant figures. Include the sign. Do NOT include units in

your answer.

1. -380

Question #: 21

A sample of gas occupies a volume of 750. mL. As it expands at a constant pressure of 755 torr, it

does 80.5  J of work on its surroundings. What is the final volume, in mL, of the gas? (1.00 L·

atm = 101.3 J) Hint: Note the units of each quantity.

    1     mL

Report your answer with four significant figures. Do NOT include units with your answer. Use

the format 2.222E2 or 2.222E-2 for answers in scientific notation.

1. 1.550E3|1.550e3|1550.|

Question #: 22

A solid, X, has a molar mass of 72.1 g/mol. In a constant-pressure calorimeter, 22.4 g of X is

dissolved in water at 20.0 °C. The mass of the solution is 296 grams.

X(s) → X(aq)

The temperature of the resulting solution rises to 27.9 °C. Assuming the solution has the same

specific heat as water (4.184 J/g °C) and there is negligible heat lost to the surroundings, what is

ΔHrxn?

.

A. 32 kJ/mol

✓B. –32 kJ/mol C. 24 kJ/mol

D. –24 kJ/mol

Question #: 23

Coal gasification converts coal into a combustible mixture of carbon monoxide andhydrogen, called coal gas, in a gasifier by the following reaction C(s) + H2O(l) CO(g) +H2(g) What is Hrxn , given: 2 C(s) + O2(g) 2 CO(g) Hrxn = 222 kJ 2 H2(g) + O2(g) 2H2O(g) Hrxn = 484 kJ H2O(l) H2O(g) Hrxn= 44 kJ

✓A. 175 kJ

B. –309 kJ C. –662 kJ D. 131 kJ

Question #: 24

Calculate ΔHrxn for the reaction:

CH4(g) + 4 Cl2(g) → CCl4(g) + 4 HCl(g)

Using the following reactions and given ΔH's:

C(s) + 2 H2(g) → CH4(g)      ΔH = –74.6 kJ

C(s) + 2 Cl2(g) → CCl4(g)     ΔH = –95.7 kJ

H2(g) + Cl2(g) → 2 HCl(g)       ΔH = –92.3 kJ

ΔHrxn =     1     kJ

1. -205.7

Question #: 25

Which chemical equation has ΔHrxno that is equal to the ΔHf

o of the product?

.

A. C3H6(g) + 9/2 O2(g) →3 CO2(g) + 3 H2O(l)

✓B. Na(s) + 1/2 I2(s) →NaI(s) C. H2(g) + Cl2(g) →2 HCl(g) D.  H2O(l) →H2(g) + 1/2 O2(g)

Question #: 26

Given the information below, what is ΔHf° for SF6

(g)?

2 CoF3(g) + SF4(g) → SF6(g) + 2 CoF2(g)    ΔHrxn° = 376 kJ/mol

.

 

A. –905 kJ/mol B. –638 kJ/mol

✓C. –1220 kJ/mol D. 2260 kJ/mol

Question #: 27

Calculate the lattice enthalpy, ΔHlattice, of silver chloride, AgCl, using the Born-Haber cycle and

the information given below.

 

Ag(s) + 1/2 Cl2(g) → AgCl(s)

 

 

 

Compound Hf° (kJ/mol)

CoF3(g) –790

SF4(g) –728

SF6(g) ?

CoF2(g) –356

Hf° AgCl(s) –127 kJ/mol

Enthalpy of sublimation, Hs° Ag(s) 284 kJ/mol

1st ionization energy (IE) of Ag(g) 731 kJ/mol

1st electron affinity (EA) of Cl(g) –349 kJ/mol

Bond dissociation energy (BE) of Cl2(g) 244 kJ/mol

A. 854 kJ/mol B. 783 kJ/mol

✓C. 915 kJ/mol D. 661 kJ/mol

Question #: 28

Use bond energies to determine the ΔHrxn for this reaction: N2(g) + 3H2(g) → 2NH3(g). Scroll

down to see all of the information.

Report your answer with three significant figures. Do NOT include units in your answer.

Bond Energies

 

ΔHrxn =     1     kJ/mol

1. -91

Question #: 29

Entropy is a state function that _____ depend on the path taken between the final and initial

states.

Entropy is defined as the ratio of heat, qrev, divided by the _____ temperature.

.

A. does; Celsius B. does; Kelvin

BondEnergy (kJ/mol)

H–H 436 H–N

390 N–N 240

C. does not; Celsius ✓D. does not; Kelvin

Question #: 30

Water (1000 g) at 50ºC is placed in a metal pan (800 g) at 25ºC.  Which statement regarding the

spontaneous heat transfer is correct?

A. Heat will be transferred from the metal to the water, so the final temperature of the water

will be higher than the final temperature of the metal. B. Heat will be transferred from the water to the metal, so the final temperature of the metal

will be higher than the final temperature of the water. C. Heat will be transferred from the metal to the water, so the final temperature of the water

will be equal to the final temperature of the metal. ✓D. Heat will be transferred from the water to the metal, so the final temperature of the metal

will be equal to the final temperature of the water.