Question 1

What is ΔH° for the following phase change?
NaCl(s)→ NaCl(l)
Substance
ΔH°f (kJ/mol)
NaCl(s)
-411.12
NaCl(l)
-385.92

Accepted Answer

A) 797.04 kJ 
B) 25.20 kJ 
C) -797.04 kJ 
D) -25.20 kJ 
E) 0 kJ 
A) 797.04 kJ 
B) 25.20 kJ 
C) -797.04 kJ 
D) -25.20 kJ 
E) 0 kJ

Question 2

Calculate the change in enthalpy when 52.0 g of solid chromium at 25°C and 1 atm pressure is oxidized.(ΔH°f for Cr2O3(s)is -1135 kJ/mol.)
4Cr(s)+ 3O2(g)→ 2Cr2O3(s)

Accepted Answer

A) -1135 kJ 
B) -284 kJ 
C) -568 kJ 
D) +1135 kJ 
E) +568 kJ 
A) -1135 kJ 
B) -284 kJ 
C) -568 kJ 
D) +1135 kJ 
E) +568 kJ

Question 3

According to the following thermochemical equation,if 403.3 g of NO2 is produced,how much heat is released at constant pressure?
2NO(g)+ O2(g)→ 2NO2(g); ΔH° = -114.4 kJ

Accepted Answer

A) 114.4 kJ 
B) 5.014 × 102 kJ 
C) 1.003 × 103 kJ 
D) 13.04 kJ 
E) 4.614 × 104 kJ 
A) 114.4 kJ 
B) 5.014 × 102 kJ 
C) 1.003 × 103 kJ 
D) 13.04 kJ 
E) 4.614 × 104 kJ

Question 4

The specific heat capacity of water(liquid)is 4.18 J/g⋅°C.What is the molar specific heat capacity of this substance? The molar mass of water is 18.01 g/mol.

Accepted Answer

A) 75.2 J/mol⋅°C 
B) 0.232 J/mol⋅°C 
C) 4.303 J/mol⋅°C 
D) 4.18 J/mol⋅°C 
E) 0.239 J/mol⋅°C 
A) 75.2 J/mol⋅°C 
B) 0.232 J/mol⋅°C 
C) 4.303 J/mol⋅°C 
D) 4.18 J/mol⋅°C 
E) 0.239 J/mol⋅°C

Question 5

Given:
Fe2O3(s)+ 3CO(g)→ 2Fe(s)+ 3CO2(g); ΔH° = -26.8 kJ
FeO(s)+ CO(g)→ Fe(s)+ CO2(g); ΔH° = -16.5 kJ
Determine ΔH° for the following thermochemical equation.
Fe2O3(s)+ CO(g)→ 2FeO(s)+ CO2(g)

Accepted Answer

A) 6.2 kJ 
B) 10.3 kJ 
C) 22.7 kJ 
D) -10.3 kJ 
E) -43.3 kJ 
A) 6.2 kJ 
B) 10.3 kJ 
C) 22.7 kJ 
D) -10.3 kJ 
E) -43.3 kJ

Question 6

At 25°C,the standard enthalpy of combustion of gaseous propane (C3H8)is -2219.0 kJ per mole of propane,and the standard enthalpy of combustion of gaseous propylene (C3H6)is -2058.3 kJ per mole of propylene.What is the standard enthalpy change for the following reaction at 25°C?
C3H6(g)+ H2(g)→ C3H8(g)
Substance
ΔH°f (kJ/mol)
CO2(g)
-393.5
H2O(l)
-285.8

Accepted Answer

A) +104.7 kJ 
B) -20.4 kJ 
C) -125.1 kJ 
D) +160.7 kJ 
E) -160.7 kJ 
A) +104.7 kJ 
B) -20.4 kJ 
C) -125.1 kJ 
D) +160.7 kJ 
E) -160.7 kJ

Question 7

Which of the following statements about heat is false?

Accepted Answer

A) If heat flows into a system,the extra energy of the system appears in the form of internal energy. 
B) A hot object possesses more heat than a cold object. 
C) If the system and surroundings are in thermal equilibrium,there is no heat flow between them. 
D) A process in which heat flows out of a system is said to be exothermic. 
E) Heat is a form of energy flow. 
A) If heat flows into a system,the extra energy of the system appears in the form of internal energy. 
B) A hot object possesses more heat than a cold object. 
C) If the system and surroundings are in thermal equilibrium,there is no heat flow between them. 
D) A process in which heat flows out of a system is said to be exothermic. 
E) Heat is a form of energy flow.

Question 8

What is the standard enthalpy of formation of liquid methylamine (CH3NH2)?
C(s)+ O2(g)→ CO2(g); ΔH° = -393.5 kJ
2H2O(l)→ 2H2(g)+ O2(g); ΔH° = 571.6 kJ  
N2(g)+ O2(g)→ NO2(g); ΔH° = 33.10 kJ
4CH3NH2(l)+ 13O2(g)→ 4CO2(g)+ 4NO2(g)+ 10H2O(l); ΔH° = -4110.4 kJ

Accepted Answer

A) +3899.2 kJ/mol 
B) -3899.2 kJ/mol 
C) -47.3 kJ/mol 
D) +47.3 kJ/mol 
E) +3178.4 kJ 
A) +3899.2 kJ/mol 
B) -3899.2 kJ/mol 
C) -47.3 kJ/mol 
D) +47.3 kJ/mol 
E) +3178.4 kJ

Question 9

What is the standard enthalpy change for the following reaction?
3CH4(g)+ 4O3(g)→ 3CO2(g)+ 6H2O(g)
Substance
ΔH°f (kJ/mol)
CH4(g)
-74)87
O3(g)
+142.7
CO2(g)
-393.5
H2O(g)
-241.8

Accepted Answer

A) -2285.1 kJ 
B) -2977.5 kJ 
C) +2977.5 kJ 
D) +2285.1 kJ 
E) -3426.5 kJ 
A) -2285.1 kJ 
B) -2977.5 kJ 
C) +2977.5 kJ 
D) +2285.1 kJ 
E) -3426.5 kJ

Question 10

Which of the following statements is incorrect concerning the thermochemical equation below?
2SO3(g)→ 2SO2(g)+ O2(g); ΔH° = 198 kJ

Accepted Answer

A) The enthalpy of the reactants exceeds that of the products. 
B) The reaction is endothermic. 
C) For the reaction 2SO2(g)+ O2(g)→ 2SO3(g),ΔH° = -198 kJ. 
D) The external pressure is 1 atm. 
E) For every mole of SO3(g)consumed,99 kJ of heat at constant pressure is consumed as well. 
A) The enthalpy of the reactants exceeds that of the products. 
B) The reaction is endothermic. 
C) For the reaction 2SO2(g)+ O2(g)→ 2SO3(g),ΔH° = -198 kJ. 
D) The external pressure is 1 atm. 
E) For every mole of SO3(g)consumed,99 kJ of heat at constant pressure is consumed as well.

Question 11

What is the change in enthalpy when 9.00 mol of sulfur trioxide decomposes to sulfur dioxide and oxygen gas?
2SO2(g)+ O2(g)→ 2SO3(g); ΔH° = 198 kJ

Accepted Answer

A) 891 kJ 
B) -198 kJ 
C) -891 kJ 
D) 198 kJ 
E) 1782 kJ 
A) 891 kJ 
B) -198 kJ 
C) -891 kJ 
D) 198 kJ 
E) 1782 kJ

Question 12

The molar heat capacity of gaseous heptane at 25.0°C is 165.2 J/(mol ∙ °C).What is its specific heat?

Accepted Answer

A) 0.6065 J/(g ∙ °
C)  
B) 1.648 J/(g ∙ °
C)  
C) 6.041 × 10-5 J/(g ∙ °
C)  
D) 165.2 J/(g ∙ °
C)  
E) 1.655 × 104 J/(g ∙ °
C)  
A) 0.6065 J/(g ∙ °
C)  
B) 1.648 J/(g ∙ °
C)  
C) 6.041 × 10-5 J/(g ∙ °
C)  
D) 165.2 J/(g ∙ °
C)  
E) 1.655 × 104 J/(g ∙ °
C)

Question 13

How much heat is gained by copper when 77.5 g of copper is warmed from 21.4°C to 75.1°C? The specific heat of copper is 0.385 J/(g ∙ °C).

Accepted Answer

A) 6.39 × 102 J 
B) 28.91 J 
C) 20.67 J 
D) 1.6 × 103 J 
E) 2.24 × 103 J 
A) 6.39 × 102 J 
B) 28.91 J 
C) 20.67 J 
D) 1.6 × 103 J 
E) 2.24 × 103 J

Question 14

Which of the following reactions corresponds to the thermochemical equation for the standard enthalpy of formation of solid strontium nitrate?

Accepted Answer

A) Sr2+(aq)+ 2NO3-(aq)→ Sr(NO3)2(s) 
B) Sr(OH)2(s)+ 2HNO3(aq)→ Sr(NO3)2(s)+ 2H2O(l) 
C) Sr(s)+ N2(g)+ 3O2(g)→ Sr(NO3)2(s) 
D) Sr(s)+ 2HNO3(aq)→ Sr(NO3)2(s)+ H2(g) 
E) Sr(s)+ 2N(g)+ 6O(g)→ Sr(NO3)2(s) 
A) Sr2+(aq)+ 2NO3-(aq)→ Sr(NO3)2(s) 
B) Sr(OH)2(s)+ 2HNO3(aq)→ Sr(NO3)2(s)+ 2H2O(l) 
C) Sr(s)+ N2(g)+ 3O2(g)→ Sr(NO3)2(s) 
D) Sr(s)+ 2HNO3(aq)→ Sr(NO3)2(s)+ H2(g) 
E) Sr(s)+ 2N(g)+ 6O(g)→ Sr(NO3)2(s)

Question 15

What is the quantity of heat evolved at constant pressure when 30.5 g H2O(l)is formed from the combustion of H2(g)and O2(g)?
H2(g)+  
O2(g)→ H2O(l); ΔH° = -285.8 kJ

Accepted Answer

A) 5.92 × 10-3 kJ 
B) 285.8 kJ 
C) 8.72 × 103 kJ 
D) 168 kJ 
E) 4.84 × 102 kJ 
A) 5.92 × 10-3 kJ 
B) 285.8 kJ 
C) 8.72 × 103 kJ 
D) 168 kJ 
E) 4.84 × 102 kJ

Question 16

A 110.0-g sample of metal at 82.00°C is added to 110.0 g of H2O(l)at 27.00°C in an insulated container.The temperature rises to 30.56°C.Neglecting the heat capacity of the container,what is the specific heat of the metal? The specific heat of H2O(l)is 4.18 J/(g ∙ °C).

Accepted Answer

A) 4.18 J/(g ∙ °
C)  
B) 60.4 J/(g ∙ °
C)  
C) 0.289 J/(g ∙ °
C)  
D) 0.28 J/(g ∙ °
C)  
E) 14.4 J/(g ∙ °
C)  
A) 4.18 J/(g ∙ °
C)  
B) 60.4 J/(g ∙ °
C)  
C) 0.289 J/(g ∙ °
C)  
D) 0.28 J/(g ∙ °
C)  
E) 14.4 J/(g ∙ °
C)

Question 17

What mass of oxygen is consumed when 285.5 kJ of energy is evolved from the combustion of a mixture of H2(g)and O2(g)?
H2(g)+  
O2(g)→ H2O(l); ΔH° = -285.8 kJ

Accepted Answer

A) 15.98 g 
B) 31.96 g 
C) 0.01564 g 
D) 31.98 g 
E) 0.01679 g 
A) 15.98 g 
B) 31.96 g 
C) 0.01564 g 
D) 31.98 g 
E) 0.01679 g

Question 18

Which of the following does not result in a change in the internal energy of the system?

Accepted Answer

A) work is done on the system 
B) work is done on the surroundings 
C) heat flows into the system 
D) heat flows to the surroundings 
E) none of the above 
A) work is done on the system 
B) work is done on the surroundings 
C) heat flows into the system 
D) heat flows to the surroundings 
E) none of the above

Question 19

The heat required to raise the temperature of 54.94 g of manganese by 1°C is called its

Accepted Answer

A) heat of vaporization. 
B) specific heat. 
C) heat of fusion. 
D) entropy. 
E) molar heat capacity. 
A) heat of vaporization. 
B) specific heat. 
C) heat of fusion. 
D) entropy. 
E) molar heat capacity.

Question 20

Which of the following has a standard enthalpy of formation value of zero at 25°C?

Accepted Answer

A) C6H12O6(s) 
B) S8(s) 
C) FeSO4(s) 
D) H2O(l) 
E) FeSO4(aq) 
A) C6H12O6(s) 
B) S8(s) 
C) FeSO4(s) 
D) H2O(l) 
E) FeSO4(aq)

Exam 6: Thermochemistry

What is ΔH° for the following phase change? NaCl(s)→ NaCl(l) Substance ΔH°f (kJ/mol) NaCl(s) -411.12 NaCl(l) -385.92

Calculate the change in enthalpy when 52.0 g of solid chromium at 25°C and 1 atm pressure is oxidized.(ΔH°f for Cr2O3(s)is -1135 kJ/mol.) 4Cr(s)+ 3O2(g)→ 2Cr2O3(s)

According to the following thermochemical equation,if 403.3 g of NO2 is produced,how much heat is released at constant pressure? 2NO(g)+ O2(g)→ 2NO2(g); ΔH° = -114.4 kJ

The specific heat capacity of water(liquid)is 4.18 J/g⋅°C.What is the molar specific heat capacity of this substance? The molar mass of water is 18.01 g/mol.

Given: Fe2O3(s)+ 3CO(g)→ 2Fe(s)+ 3CO2(g); ΔH° = -26.8 kJ FeO(s)+ CO(g)→ Fe(s)+ CO2(g); ΔH° = -16.5 kJ Determine ΔH° for the following thermochemical equation. Fe2O3(s)+ CO(g)→ 2FeO(s)+ CO2(g)

Which of the following statements about heat is false?

What is the standard enthalpy of formation of liquid methylamine (CH3NH2)? C(s)+ O2(g)→ CO2(g); ΔH° = -393.5 kJ 2H2O(l)→ 2H2(g)+ O2(g); ΔH° = 571.6 kJ N2(g)+ O2(g)→ NO2(g); ΔH° = 33.10 kJ 4CH3NH2(l)+ 13O2(g)→ 4CO2(g)+ 4NO2(g)+ 10H2O(l); ΔH° = -4110.4 kJ

What is the standard enthalpy change for the following reaction? 3CH4(g)+ 4O3(g)→ 3CO2(g)+ 6H2O(g) Substance ΔH°f (kJ/mol) CH4(g) -74)87 O3(g) +142.7 CO2(g) -393.5 H2O(g) -241.8

Which of the following statements is incorrect concerning the thermochemical equation below? 2SO3(g)→ 2SO2(g)+ O2(g); ΔH° = 198 kJ

What is the change in enthalpy when 9.00 mol of sulfur trioxide decomposes to sulfur dioxide and oxygen gas? 2SO2(g)+ O2(g)→ 2SO3(g); ΔH° = 198 kJ

The molar heat capacity of gaseous heptane at 25.0°C is 165.2 J/(mol ∙ °C).What is its specific heat?

How much heat is gained by copper when 77.5 g of copper is warmed from 21.4°C to 75.1°C? The specific heat of copper is 0.385 J/(g ∙ °C).

Which of the following reactions corresponds to the thermochemical equation for the standard enthalpy of formation of solid strontium nitrate?

What is the quantity of heat evolved at constant pressure when 30.5 g H2O(l)is formed from the combustion of H2(g)and O2(g)? H2(g)+ O2(g)→ H2O(l); ΔH° = -285.8 kJ

A 110.0-g sample of metal at 82.00°C is added to 110.0 g of H2O(l)at 27.00°C in an insulated container.The temperature rises to 30.56°C.Neglecting the heat capacity of the container,what is the specific heat of the metal? The specific heat of H2O(l)is 4.18 J/(g ∙ °C).

What mass of oxygen is consumed when 285.5 kJ of energy is evolved from the combustion of a mixture of H2(g)and O2(g)? H2(g)+ O2(g)→ H2O(l); ΔH° = -285.8 kJ

Which of the following does not result in a change in the internal energy of the system?

The heat required to raise the temperature of 54.94 g of manganese by 1°C is called its

Which of the following has a standard enthalpy of formation value of zero at 25°C?

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What is ΔH° for the following phase change? NaCl(s)→ NaCl(l) Substance ΔH°_f (kJ/mol) NaCl(s) -411.12 NaCl(l) -385.92

Calculate the change in enthalpy when 52.0 g of solid chromium at 25°C and 1 atm pressure is oxidized.(ΔH°_f for Cr₂O₃(s)is -1135 kJ/mol.) 4Cr(s)+ 3O₂(g)→ 2Cr₂O₃(s)

According to the following thermochemical equation,if 403.3 g of NO₂ is produced,how much heat is released at constant pressure? 2NO(g)+ O₂(g)→ 2NO₂(g); ΔH° = -114.4 kJ

Given: Fe₂O₃(s)+ 3CO(g)→ 2Fe(s)+ 3CO₂(g); ΔH° = -26.8 kJ FeO(s)+ CO(g)→ Fe(s)+ CO₂(g); ΔH° = -16.5 kJ Determine ΔH° for the following thermochemical equation. Fe₂O₃(s)+ CO(g)→ 2FeO(s)+ CO₂(g)

What is the standard enthalpy change for the following reaction? 3CH₄(g)+ 4O₃(g)→ 3CO₂(g)+ 6H₂O(g) Substance ΔH°_f (kJ/mol) CH₄(g) -74)87 O₃(g) +142.7 CO₂(g) -393.5 H₂O(g) -241.8

Which of the following statements is incorrect concerning the thermochemical equation below? 2SO₃(g)→ 2SO₂(g)+ O₂(g); ΔH° = 198 kJ

What is the change in enthalpy when 9.00 mol of sulfur trioxide decomposes to sulfur dioxide and oxygen gas? 2SO₂(g)+ O₂(g)→ 2SO₃(g); ΔH° = 198 kJ

What is the quantity of heat evolved at constant pressure when 30.5 g H₂O(l)is formed from the combustion of H₂(g)and O₂(g)? H₂(g)+ O₂(g)→ H₂O(l); ΔH° = -285.8 kJ

A 110.0-g sample of metal at 82.00°C is added to 110.0 g of H₂O(l)at 27.00°C in an insulated container.The temperature rises to 30.56°C.Neglecting the heat capacity of the container,what is the specific heat of the metal? The specific heat of H₂O(l)is 4.18 J/(g ∙ °C).

What mass of oxygen is consumed when 285.5 kJ of energy is evolved from the combustion of a mixture of H₂(g)and O₂(g)? H₂(g)+ O₂(g)→ H₂O(l); ΔH° = -285.8 kJ