Question 1

Using Hess's law, what is ΔH°rxn for the following reaction? NO(g) + O(g) → NO2(g)

Accepted Answer

A)  -839.8 kJ/mol 
B)  -306.0 kJ/mol 
C)  157.9 kJ/mol 
D)  394.9 kJ/mol 
E)  442.3 kJ/mol 
A)  -839.8 kJ/mol 
B)  -306.0 kJ/mol 
C)  157.9 kJ/mol 
D)  394.9 kJ/mol 
E)  442.3 kJ/mol

Question 2

A 275-g sample of nickel at l00.0°C is placed in 100.0 g of water at 22.0°C. What is the final temperature of the water? Assume no heat transfer with the surroundings. The specific heat of nickel is 0.444 J/g·°C and the specific heat of water is 4.184 J/g·°C.

Accepted Answer

A)  39.6°C 
B)  40.8°C 
C)  61.0°C 
D)  79.2°C 
E)  82.4°C 
A)  39.6°C 
B)  40.8°C 
C)  61.0°C 
D)  79.2°C 
E)  82.4°C

Question 3

Which equation has a ΔHrxn that is not equal to ΔHof of the product?

Accepted Answer

A)  F2(g) + ½O2(g) → F2O(g) 
B)  O2(g) + 2H2(g) → 2H2O(g) 
C)  H2(g) + ½O2(g) + → H2O(l) 
D)  Ti(s) + 2Cl2(g) → TiCl4(l) 
E)  ½H2(g) + ½Cl2(g) → HCl(g) 
A)  F2(g) + ½O2(g) → F2O(g) 
B)  O2(g) + 2H2(g) → 2H2O(g) 
C)  H2(g) + ½O2(g) + → H2O(l) 
D)  Ti(s) + 2Cl2(g) → TiCl4(l) 
E)  ½H2(g) + ½Cl2(g) → HCl(g)

Question 4

The combustion of pentane produces heat according to the following thermochemical equation. C5H12(l) + 8O2(g) → 5CO2(g) + 6H2O(l) ΔH°rxn= -3510 kJ/mol
How many grams of CO2 is produced per 2.50 × 103 kJ of heat released?

Accepted Answer

A)  6.27 g 
B)  31.3 g 
C)  61.8 g 
D)  157 g 
E)  220 g 
A)  6.27 g 
B)  31.3 g 
C)  61.8 g 
D)  157 g 
E)  220 g

Question 5

How much heat is required to raise the temperature of 22.8 g of copper from 20.0°C to 875.0°C? The specific heat of copper is 0.385 J/g·°C.

Accepted Answer

A)  14.4 J 
B)  176 J 
C)  7.51 kJ 
D)  7.68 kJ 
E)  9.90 kJ 
A)  14.4 J 
B)  176 J 
C)  7.51 kJ 
D)  7.68 kJ 
E)  9.90 kJ

Question 6

What is ΔH°rxn for the following reaction? C6H6(l) + 15/2 O2(g) → 6CO2(g) + 3H2O(l)
6C(graphite) + 3H2(g) → C6H6(l) ΔH°rxn = +49.0 kJ/mol
C(graphite) + O2(g) → CO2(g) ΔH°rxn = -393.5 kJ/mol
H2(g) + ½O2(g) → H2O(l) ΔH°rxn = -285.8 kJ/mol

Accepted Answer

A)  -630.3 kJ/mol 
B)  -2597.8 kJ/mol 
C)  -3169.4kJ/mol 
D)  -3267.4 kJ/mol 
E)  630.3 kJ/mol 
A)  -630.3 kJ/mol 
B)  -2597.8 kJ/mol 
C)  -3169.4kJ/mol 
D)  -3267.4 kJ/mol 
E)  630.3 kJ/mol

Question 7

Cold packs, whose temperatures are lowered when ammonium nitrate dissolves in water, are carried by athletic trainers when transporting ice is not possible. Which of the following is true of this reaction?

Accepted Answer

A)  ΔH 0, process is exothermic 
C)  ΔH 0, process is endothermic 
E)  ΔH = 0, since cold packs are sealed 
A)  ΔH 0, process is exothermic 
C)  ΔH 0, process is endothermic 
E)  ΔH = 0, since cold packs are sealed

Question 8

Clearly state the thermodynamic standard state of
a. an element or compound.
b. a solute.

Accepted Answer

a. Standard state is the stabl

Question 9

If two solutions are mixed together in a container and the container "feels hot", then

Accepted Answer

A)  the reaction is endothermic. 
B)  the reaction is exothermic. 
C)  the energy of the universe is increased. 
D)  the energy of both the system and the surroundings is decreased. 
E)  the energy of the system is increased. 
A)  the reaction is endothermic. 
B)  the reaction is exothermic. 
C)  the energy of the universe is increased. 
D)  the energy of both the system and the surroundings is decreased. 
E)  the energy of the system is increased.

Question 10

What is ΔH°rxn for the following reaction? NO2(g) + CO(g) → CO2(g) + NO(g)

Accepted Answer

A)  339.6 kJ 
B)  379.8 kJ 
C)  -226.5 kJ 
D)  -339.6 kJ 
E)  -379.8 kJ 
A)  339.6 kJ 
B)  379.8 kJ 
C)  -226.5 kJ 
D)  -339.6 kJ 
E)  -379.8 kJ

Question 11

The standard temperature is ________; the standard concentration of a solution is ________; and the standard pressure is ________.

Accepted Answer

usually 25

Question 12

A glass containing 200.0 g of H2O at 20.0°C was placed in a refrigerator. The water loses 11.7 kJ of heat as it cools to a constant temperature. What is its new temperature? The specific heat of water is 4.184 J/g·°C.

Accepted Answer

A)  0.0°C 
B)  4.0°C 
C)  6.0°C 
D)  14.0°C 
E)  34.0°C 
A)  0.0°C 
B)  4.0°C 
C)  6.0°C 
D)  14.0°C 
E)  34.0°C

Question 13

A 307-g sample of an unknown mineral was heated to 98.7°C and placed into a calorimeter containing 72.4 g of water at 23.6°C. The heat capacity of the calorimeter was 15.7 J/°C. The final temperature in the calorimeter was 32.4°C. What is the specific heat capacity of the mineral?

Accepted Answer

A)  0.124 J/g·°C 
B)  0.131 J/g·°C 
C)  0.138 J/g·°C 
D)  0.145 J/g·°C 
E)  None of these choices is correct. 
A)  0.124 J/g·°C 
B)  0.131 J/g·°C 
C)  0.138 J/g·°C 
D)  0.145 J/g·°C 
E)  None of these choices is correct.

Question 14

A system contracts from an initial volume of 15.0 L to a final volume of 10.0 L under a constant external pressure of 0.80 atm. What is w? (1 L·atm = 101.3 J)

Accepted Answer

A)  -4.0 J 
B)  +4.0 J 
C)  -4.1 ×102 J 
D)  +4.1 ×102 J 
E)  +81 J 
A)  -4.0 J 
B)  +4.0 J 
C)  -4.1 ×102 J 
D)  +4.1 ×102 J 
E)  +81 J

Question 15

Suppose a new metallic element X is discovered, and its reactions with oxygen gas and chlorine gas at 298 K are studied.   However, it is later discovered that one of the samples was contaminated, and the ΔHºrxn value from this trial is not reliable. Which trial had the contaminated sample, and what should the correct value of ΔHºrxn be for this trial?

Accepted Answer

A)  Trial 1 had the contaminated sample; its ΔHºrxn value should be -900 kJ/mol. 
B)  Trial 2 had the contaminated sample; its ΔHºrxn value should be +100 kJ/mol. 
C)  Trial 3 had the contaminated sample; its ΔHºrxn value should be -1000 kJ/mol. 
D)  Trial 3 had the contaminated sample; its ΔHºrxn value should be +1000 kJ/mol. 
E)  Not enough information is provided; all three trials must be redone. 
A)  Trial 1 had the contaminated sample; its ΔHºrxn value should be -900 kJ/mol. 
B)  Trial 2 had the contaminated sample; its ΔHºrxn value should be +100 kJ/mol. 
C)  Trial 3 had the contaminated sample; its ΔHºrxn value should be -1000 kJ/mol. 
D)  Trial 3 had the contaminated sample; its ΔHºrxn value should be +1000 kJ/mol. 
E)  Not enough information is provided; all three trials must be redone.

Question 16

Given that CaO(s) + H2O(l) → Ca(OH)2(s), ΔH°rxn = -64.8 kJ/mol, how many grams of CaO must react in order to liberate 525 kJ of heat?

Accepted Answer

A)  6.92 g 
B)  56.1 g 
C)  454 g 
D)  606 g 
E)  3.40 × 104 g 
A)  6.92 g 
B)  56.1 g 
C)  454 g 
D)  606 g 
E)  3.40 × 104 g

Question 17

For which of the substances below is ΔHof = 0?

Accepted Answer

A)  O2(g) 
B)  N2(l) 
C)  Na(g) 
D)  Xe(l) 
A)  O2(g) 
B)  N2(l) 
C)  Na(g) 
D)  Xe(l)

Question 18

Pentaborane B5H9(s) burns vigorously in O2 to give B2O3(s) and H2O(l). What is ΔH° for the combustion of 1 mol of B5H9(s)? Substance ΔH°f (kJ/mol)
B2O3(s) -1273.5
B5H9(s) +73.2
H2O(l) -285.8

Accepted Answer

A)  -1.5 × 103 kJ 
B)  -1.6× 103 kJ 
C)  -4.4 × 103 kJ 
D)  -4.7× 103 kJ 
E)  -9.0× 103 kJ 
A)  -1.5 × 103 kJ 
B)  -1.6× 103 kJ 
C)  -4.4 × 103 kJ 
D)  -4.7× 103 kJ 
E)  -9.0× 103 kJ

Question 19

When heat is absorbed by the system and work is done by the system on the surroundings then

Accepted Answer

A)  q is negative and w is positive. 
B)  both q and w are positive. 
C)  both q and w are negative. 
D)  q is positive and w is negative. 
E)  both q and w are zero. 
A)  q is negative and w is positive. 
B)  both q and w are positive. 
C)  both q and w are negative. 
D)  q is positive and w is negative. 
E)  both q and w are zero.

Question 20

Atoms A and Z may form either single bonds or double bonds. Shown is an energy diagram for the formation of a single bond between A and Z from the individual atoms in the gas phase.   Which diagram below corresponds to the reaction A(g) + Z(g) → A=Z(g)?

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Exam 5: Thermochemistry

Using Hess's law, what is ΔH°rxn for the following reaction? NO(g) + O(g) → NO2(g)

A 275-g sample of nickel at l00.0°C is placed in 100.0 g of water at 22.0°C. What is the final temperature of the water? Assume no heat transfer with the surroundings. The specific heat of nickel is 0.444 J/g·°C and the specific heat of water is 4.184 J/g·°C.

Which equation has a ΔHrxn that is not equal to ΔHof of the product?

The combustion of pentane produces heat according to the following thermochemical equation. C5H12(l) + 8O2(g) → 5CO2(g) + 6H2O(l) ΔH°rxn= -3510 kJ/mol How many grams of CO2 is produced per 2.50 × 103 kJ of heat released?

How much heat is required to raise the temperature of 22.8 g of copper from 20.0°C to 875.0°C? The specific heat of copper is 0.385 J/g·°C.

What is ΔH°rxn for the following reaction? C6H6(l) + 15/2 O2(g) → 6CO2(g) + 3H2O(l) 6C(graphite) + 3H2(g) → C6H6(l) ΔH°rxn = +49.0 kJ/mol C(graphite) + O2(g) → CO2(g) ΔH°rxn = -393.5 kJ/mol H2(g) + ½O2(g) → H2O(l) ΔH°rxn = -285.8 kJ/mol

Cold packs, whose temperatures are lowered when ammonium nitrate dissolves in water, are carried by athletic trainers when transporting ice is not possible. Which of the following is true of this reaction?

Clearly state the thermodynamic standard state of a. an element or compound. b. a solute.

If two solutions are mixed together in a container and the container "feels hot", then

What is ΔH°rxn for the following reaction? NO2(g) + CO(g) → CO2(g) + NO(g)

The standard temperature is ________; the standard concentration of a solution is ________; and the standard pressure is ________.

A glass containing 200.0 g of H2O at 20.0°C was placed in a refrigerator. The water loses 11.7 kJ of heat as it cools to a constant temperature. What is its new temperature? The specific heat of water is 4.184 J/g·°C.

A 307-g sample of an unknown mineral was heated to 98.7°C and placed into a calorimeter containing 72.4 g of water at 23.6°C. The heat capacity of the calorimeter was 15.7 J/°C. The final temperature in the calorimeter was 32.4°C. What is the specific heat capacity of the mineral?

A system contracts from an initial volume of 15.0 L to a final volume of 10.0 L under a constant external pressure of 0.80 atm. What is w? (1 L·atm = 101.3 J)

Given that CaO(s) + H2O(l) → Ca(OH)2(s), ΔH°rxn = -64.8 kJ/mol, how many grams of CaO must react in order to liberate 525 kJ of heat?

For which of the substances below is ΔHof = 0?

Pentaborane B5H9(s) burns vigorously in O2 to give B2O3(s) and H2O(l). What is ΔH° for the combustion of 1 mol of B5H9(s)? Substance ΔH°f (kJ/mol) B2O3(s) -1273.5 B5H9(s) +73.2 H2O(l) -285.8

When heat is absorbed by the system and work is done by the system on the surroundings then

Atoms A and Z may form either single bonds or double bonds. Shown is an energy diagram for the formation of a single bond between A and Z from the individual atoms in the gas phase. Which diagram below corresponds to the reaction A(g) + Z(g) → A=Z(g)?

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Reactions in Aqueous Solutions

Quantum Theory and the Electronic Structure of Atoms

Electron Configuration and the Periodic Table

Chemical Bonding I: Basic Concepts

Chemical Bonding II: Molecular Geometry and Bonding Theories

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Intermolecular Forces and the Physical Properties of Liquids and Solids

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Entropy, Free Energy, and Equilibrium

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Filters

Using Hess's law, what is ΔH°_rxn for the following reaction? NO(g) + O(g) → NO₂(g)

Which equation has a ΔH_rxnthat is not equal to ΔH^o_f of the product?

The combustion of pentane produces heat according to the following thermochemical equation. C₅H₁₂(l) + 8O₂(g) → 5CO₂(g) + 6H₂O(l) ΔH°_rxn= -3510 kJ/mol How many grams of CO₂is produced per 2.50 × 10³ kJ of heat released?

What is ΔH°_rxn for the following reaction? C₆H₆(l) + 15/2 O₂(g) → 6CO₂(g) + 3H₂O(l) 6C(graphite) + 3H₂(g) → C₆H₆(l) ΔH°_rxn = +49.0 kJ/mol C(graphite) + O₂(g) → CO₂(g) ΔH°_rxn = -393.5 kJ/mol H₂(g) + ½O₂(g) → H₂O(l) ΔH°_rxn = -285.8 kJ/mol

What is ΔH°_rxnfor the following reaction? NO₂(g) + CO(g) → CO₂(g) + NO(g)

The standard temperature is ; the standard concentration of a solution is ; and the standard pressure is .

A glass containing 200.0 g of H₂O at 20.0°C was placed in a refrigerator. The water loses 11.7 kJ of heat as it cools to a constant temperature. What is its new temperature? The specific heat of water is 4.184 J/g·°C.

Given that CaO(s) + H₂O(l) → Ca(OH)₂(s), ΔH°_rxn = -64.8 kJ/mol, how many grams of CaO must react in order to liberate 525 kJ of heat?

For which of the substances below is ΔH^o_f = 0?

Pentaborane B₅H₉(s) burns vigorously in O₂ to give B₂O₃(s) and H₂O(l). What is ΔH° for the combustion of 1 mol of B₅H₉(s)? Substance ΔH°_f (kJ/mol) B₂O₃(s) -1273.5 B₅H₉(s) +73.2 H₂O(l) -285.8