Question 1

Given w = 0, an endothermic reaction has the following properties:

Accepted Answer

A) +ΔH and -ΔU 
B) -ΔH and +ΔU 
C) +ΔH and +ΔU 
D) -ΔH and -ΔU 
A) +ΔH and -ΔU 
B) -ΔH and +ΔU 
C) +ΔH and +ΔU 
D) -ΔH and -ΔU

Question 2

A piece of iron (mass = 25.0 g)at 398 K is placed in a styrofoam coffee cup containing 25.0 mL of water at 298 K. Assuming that no heat is lost to the cup or the surroundings, what will the final temperature of the water be? The specific heat capacity of iron = 0.449 J g-1 °C-1 and water = 4.184 J g-1 °C-1.

Accepted Answer

A) 348 K 
B) 308 K 
C) 287 K 
D) 325 K 
E) 388 K 
A) 348 K 
B) 308 K 
C) 287 K 
D) 325 K 
E) 388 K

Question 3

Match the following.

-+w

Accepted Answer

A) the system loses thermal energy to the surroundings 
B) work done on the system by the surroundings 
C) energy flows into the system from the surroundings 
D) the system gains thermal energy from the surroundings 
E) energy flows out of the system into the surroundings
F)work done by the system on the surroundings 
A) the system loses thermal energy to the surroundings 
B) work done on the system by the surroundings 
C) energy flows into the system from the surroundings 
D) the system gains thermal energy from the surroundings 
E) energy flows out of the system into the surroundings
F)work done by the system on the surroundings

Question 4

An unknown metal alloy, specific heat capacity = 0.613 J g-1 °C-1, has a temperature change of 31.02 to 24.77 °C after a heat transfer of -106.4 J. Calculate the mass of the alloy in question.

Accepted Answer

A) 16.8 g 
B) 12.7 g 
C) 38.3 g 
D) 27.8 g 
E) 9.17 g 
A) 16.8 g 
B) 12.7 g 
C) 38.3 g 
D) 27.8 g 
E) 9.17 g

Question 5

Use the information provided to determine ΔrH° for the following reaction: ΔfH° (kJ mol-1)3Fe2O3(s)+ CO(g)→ 2Fe3O4(s)+ CO2(g)ΔrH° = ?
Fe2O3(s)-824
Fe3O4(s)-1118
CO(g) -111
CO2(g) -394

Accepted Answer

A) +277 kJ mol-1 
B) -577 kJ mol-1 
C) -47 kJ mol-1 
D) +144 kJ mol-1 
E) -111 kJ mol-1 
A) +277 kJ mol-1 
B) -577 kJ mol-1 
C) -47 kJ mol-1 
D) +144 kJ mol-1 
E) -111 kJ mol-1

Question 6

Using the following equation for the combustion of octane, calculate the heat of reaction for 100.0 g of octane. The molar mass of octane is 114.33 g mol-1. 2C8H18 + 25O2 → 16CO2 + 18H2O ΔrH° = -11018 kJ

Accepted Answer

A) 4.82 × 103 kJ 
B) 4.82 kJ 
C) 9.64 × 103 kJ 
D) 1.26 × 104 kJ 
A) 4.82 × 103 kJ 
B) 4.82 kJ 
C) 9.64 × 103 kJ 
D) 1.26 × 104 kJ

Question 7

For a process at constant pressure, 49,600 calories of heat are released. This quantity of heat is equivalent to

Accepted Answer

A) 4.82 × 10-6 J. 
B) 1.19 × 104 J. 
C) 1.24 × 104 J. 
D) 2.08 × 105 J. 
A) 4.82 × 10-6 J. 
B) 1.19 × 104 J. 
C) 1.24 × 104 J. 
D) 2.08 × 105 J.

Question 8

Calculate the change in internal energy (ΔU)for a system that is absorbing 35.8 kJ of heat and is expanding from 8.00 to 24.0 L in volume at 1.00 bar. (Remember that 100 J = 1 L bar)

Accepted Answer

A) +51.8 kJ 
B) -15.8 kJ 
C) -16.6 kJ 
D) -29.3 kJ 
E) +34.2 kJ 
A) +51.8 kJ 
B) -15.8 kJ 
C) -16.6 kJ 
D) -29.3 kJ 
E) +34.2 kJ

Question 9

Using the following equation for the combustion of octane, calculate the amount of moles of carbon dioxide formed from 100.0 g of octane. The molar mass of octane is 114.33 g mol-1. The molar mass of carbon dioxide is 44.0095 g mol-1. 2C8H18 + 25O2 → 16CO2 + 18H2O ΔrH° = -11018 kJ

Accepted Answer

A) 18.18 moles 
B) 6.997 moles 
C) 14.00 moles 
D) 8.000 moles 
E) 10.93 moles 
A) 18.18 moles 
B) 6.997 moles 
C) 14.00 moles 
D) 8.000 moles 
E) 10.93 moles

Question 10

Match the following.

-+ q

Accepted Answer

A) the system loses thermal energy to the surroundings 
B) work done on the system by the surroundings 
C) energy flows into the system from the surroundings 
D) the system gains thermal energy from the surroundings 
E) energy flows out of the system into the surroundings
F)work done by the system on the surroundings 
A) the system loses thermal energy to the surroundings 
B) work done on the system by the surroundings 
C) energy flows into the system from the surroundings 
D) the system gains thermal energy from the surroundings 
E) energy flows out of the system into the surroundings
F)work done by the system on the surroundings

Question 11

Choose the reaction that illustrates ΔfH° for Ca(NO3)2.

Accepted Answer

A) Ca(s)+ N2(g)+ 3O2(g)→ Ca(NO3)2(s) 
B) Ca2+(aq)+ 2NO3-(aq)→ Ca(NO3)2(aq) 
C) Ca(s)+ 2N(g)+ 6O(g)→ Ca(NO3)2(s) 
D) Ca(NO3)2(aq)→ Ca2+(aq)+ 2NO3-(aq) 
E) Ca(NO3)2(s)→ Ca(s)+ N2(g)+ 3O2(g) 
A) Ca(s)+ N2(g)+ 3O2(g)→ Ca(NO3)2(s) 
B) Ca2+(aq)+ 2NO3-(aq)→ Ca(NO3)2(aq) 
C) Ca(s)+ 2N(g)+ 6O(g)→ Ca(NO3)2(s) 
D) Ca(NO3)2(aq)→ Ca2+(aq)+ 2NO3-(aq) 
E) Ca(NO3)2(s)→ Ca(s)+ N2(g)+ 3O2(g)

Question 12

Calculate the internal energy change, ΔrU, for the combustion of 29.3 g of vitamin C (C6H8O6, molar mass = 176.124 g mol-1)if the combustion inside a bomb calorimeter, Ccal = 8.31 kJ °C-1, causes a temperature change from 21.5 °C to 68.3 °C.

Accepted Answer

A) -1.78 × 103 kJ mol-1 
B) -2.34 × 103 kJ mol-1 
C) -6.03 × 103 kJ mol-1 
D) -9.19 × 102 kJ mol-1 
E) -1.67 × 102 kJ mol-1 
A) -1.78 × 103 kJ mol-1 
B) -2.34 × 103 kJ mol-1 
C) -6.03 × 103 kJ mol-1 
D) -9.19 × 102 kJ mol-1 
E) -1.67 × 102 kJ mol-1

Question 13

Calculate the heat transfer, in J, when 5.00 g of chromium (specific heat capacity = 0.449 J g-1 °C-1)at 0.00 °C is placed in 50.0 mL of water. The final temperature of the water is 23.8 °C. The chromium is defined as the system in this scenario.

Accepted Answer

A) -53 J 
B) 53 J 
C) 82 J 
D) -82 J 
E) 93 J 
A) -53 J 
B) 53 J 
C) 82 J 
D) -82 J 
E) 93 J

Question 14

Calculate the change in internal energy (ΔU)for a system that is giving off 45.0 kJ of heat and is performing 855 J of work on the surroundings.

Accepted Answer

A) 44.1 kJ 
B) -44.1 kJ 
C) -45.9 kJ 
D) 9.00 × 102 kJ 
E) -9.00 × 102 kJ 
A) 44.1 kJ 
B) -44.1 kJ 
C) -45.9 kJ 
D) 9.00 × 102 kJ 
E) -9.00 × 102 kJ

Question 15

A chemist wishes to calibrate a bomb calorimeter, so she combusts 5.58 g of 4-pentenoic acid, ΔcombustionU = -26.77 kJ g-1, which causes a temperature change from 23.4 °C to 38.9 °C. What should the chemist report for the value of Ccal?

Accepted Answer

A) 6.10 kJ °C-1 
B) 17.5 kJ °C-1 
C) 28.7 kJ °C-1 
D) 9.67 kJ °C-1 
E) 7.61 kJ °C-1 
A) 6.10 kJ °C-1 
B) 17.5 kJ °C-1 
C) 28.7 kJ °C-1 
D) 9.67 kJ °C-1 
E) 7.61 kJ °C-1

Question 16

Use the standard reaction enthalpies given below to determine ΔrH° for the following reaction: 2S(s)+ 3O2(g)→ 2SO3(g) ΔrH° = ?
Given:
SO2(g)→ S(s)+ O2(g) ΔrH° = +296.8 kJ
2SO2(g)+ O2(g)→ 2SO3(g)ΔrH° = -197.8 kJ

Accepted Answer

A) -494.6 kJ mol-1 
B) -692.4 kJ mol-1 
C) -791.4 kJ mol-1 
D) 1583 kJ mol-1 
E) -293.0 kJ mol-1 
A) -494.6 kJ mol-1 
B) -692.4 kJ mol-1 
C) -791.4 kJ mol-1 
D) 1583 kJ mol-1 
E) -293.0 kJ mol-1

Question 17

Using the following thermochemical equation, determine the amount of heat produced from the combustion of 24.3 g benzene (C6H6). The molar mass of benzene is 78.11 g mol-1 2C6H6(l)+ 15O2(g)→ 12CO2(g)+ 6H2O(g)ΔrH° = -6278 kJ

Accepted Answer

A) 3910 kJ C6H6 
B) 1950 kJ C6H6 
C) 977 kJ C6H6 
D) 40.1 kJ C6H6 
E) 0.302 kJ C6H6 
A) 3910 kJ C6H6 
B) 1950 kJ C6H6 
C) 977 kJ C6H6 
D) 40.1 kJ C6H6 
E) 0.302 kJ C6H6

Question 18

Calculate the internal energy change, ΔrU, for the combustion of 6.9261 g of diethylene glycol (C4H10O3, molar mass = 106.120 g mol-1)if the combustion inside a bomb calorimeter, Ccal = 13.84 kJ °C-1, causes a temperature change from 22.8 °C to 34.0 °C.

Accepted Answer

A) -4.39 × 103 kJ mol-1 
B) -9.16 × 102 kJ mol-1 
C) -2.37 × 103 kJ mol-1 
D) 4.39 × 103 kJ mol-1 
E) 1.18 × 103 kJ mol-1 
A) -4.39 × 103 kJ mol-1 
B) -9.16 × 102 kJ mol-1 
C) -2.37 × 103 kJ mol-1 
D) 4.39 × 103 kJ mol-1 
E) 1.18 × 103 kJ mol-1

Question 19

Identify what a bomb calorimeter measures.

Accepted Answer

A) measures ΔH for aqueous solutions 
B) measures ΔU for combustion reactions 
C) measures ΔH for oxidation solutions 
D) measures ΔT for hydrolysis solutions 
E) measures ΔU for reduction reactions 
A) measures ΔH for aqueous solutions 
B) measures ΔU for combustion reactions 
C) measures ΔH for oxidation solutions 
D) measures ΔT for hydrolysis solutions 
E) measures ΔU for reduction reactions

Question 20

The specific heat capacity of solid copper metal is 0.385 J g-1 K-1. How many joules of heat are needed to raise the temperature of a 1.55 kg block of copper from 33.0 °C to 77.5 °C?

Accepted Answer

A) 1.79 × 105 J 
B) 26.6 J 
C) 2.66 × 104 J 
D) 5.58 × 10-6 J 
E) 0.00558 J 
A) 1.79 × 105 J 
B) 26.6 J 
C) 2.66 × 104 J 
D) 5.58 × 10-6 J 
E) 0.00558 J

Exam 6: Thermochemistry

Given w = 0, an endothermic reaction has the following properties:

Match the following. -+w

An unknown metal alloy, specific heat capacity = 0.613 J g-1 °C-1, has a temperature change of 31.02 to 24.77 °C after a heat transfer of -106.4 J. Calculate the mass of the alloy in question.

Use the information provided to determine ΔrH° for the following reaction: ΔfH° (kJ mol-1)3Fe2O3(s)+ CO(g)→ 2Fe3O4(s)+ CO2(g)ΔrH° = ? Fe2O3(s)-824 Fe3O4(s)-1118 CO(g) -111 CO2(g) -394

Using the following equation for the combustion of octane, calculate the heat of reaction for 100.0 g of octane. The molar mass of octane is 114.33 g mol-1. 2C8H18 + 25O2 → 16CO2 + 18H2O ΔrH° = -11018 kJ

For a process at constant pressure, 49,600 calories of heat are released. This quantity of heat is equivalent to

Calculate the change in internal energy (ΔU)for a system that is absorbing 35.8 kJ of heat and is expanding from 8.00 to 24.0 L in volume at 1.00 bar. (Remember that 100 J = 1 L bar)

Using the following equation for the combustion of octane, calculate the amount of moles of carbon dioxide formed from 100.0 g of octane. The molar mass of octane is 114.33 g mol-1. The molar mass of carbon dioxide is 44.0095 g mol-1. 2C8H18 + 25O2 → 16CO2 + 18H2O ΔrH° = -11018 kJ

Match the following. -+ q

Choose the reaction that illustrates ΔfH° for Ca(NO3)2.

Calculate the internal energy change, ΔrU, for the combustion of 29.3 g of vitamin C (C6H8O6, molar mass = 176.124 g mol-1)if the combustion inside a bomb calorimeter, Ccal = 8.31 kJ °C-1, causes a temperature change from 21.5 °C to 68.3 °C.

Calculate the heat transfer, in J, when 5.00 g of chromium (specific heat capacity = 0.449 J g-1 °C-1)at 0.00 °C is placed in 50.0 mL of water. The final temperature of the water is 23.8 °C. The chromium is defined as the system in this scenario.

Calculate the change in internal energy (ΔU)for a system that is giving off 45.0 kJ of heat and is performing 855 J of work on the surroundings.

A chemist wishes to calibrate a bomb calorimeter, so she combusts 5.58 g of 4-pentenoic acid, ΔcombustionU = -26.77 kJ g-1, which causes a temperature change from 23.4 °C to 38.9 °C. What should the chemist report for the value of Ccal?

Use the standard reaction enthalpies given below to determine ΔrH° for the following reaction: 2S(s)+ 3O2(g)→ 2SO3(g) ΔrH° = ? Given: SO2(g)→ S(s)+ O2(g) ΔrH° = +296.8 kJ 2SO2(g)+ O2(g)→ 2SO3(g)ΔrH° = -197.8 kJ

Using the following thermochemical equation, determine the amount of heat produced from the combustion of 24.3 g benzene (C6H6). The molar mass of benzene is 78.11 g mol-1 2C6H6(l)+ 15O2(g)→ 12CO2(g)+ 6H2O(g)ΔrH° = -6278 kJ

Calculate the internal energy change, ΔrU, for the combustion of 6.9261 g of diethylene glycol (C4H10O3, molar mass = 106.120 g mol-1)if the combustion inside a bomb calorimeter, Ccal = 13.84 kJ °C-1, causes a temperature change from 22.8 °C to 34.0 °C.

Identify what a bomb calorimeter measures.

The specific heat capacity of solid copper metal is 0.385 J g-1 K-1. How many joules of heat are needed to raise the temperature of a 1.55 kg block of copper from 33.0 °C to 77.5 °C?

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An unknown metal alloy, specific heat capacity = 0.613 J g^-1 °C^-1, has a temperature change of 31.02 to 24.77 °C after a heat transfer of -106.4 J. Calculate the mass of the alloy in question.

Use the information provided to determine Δ_rH° for the following reaction: Δ_fH° (kJ mol^-1)3Fe₂O₃(s)+ CO(g)→ 2Fe₃O₄(s)+ CO₂(g)Δ_rH°= ? Fe₂O₃(s)-824 Fe₃O₄(s)-1118 CO(g) -111 CO₂(g) -394

Using the following equation for the combustion of octane, calculate the heat of reaction for 100.0 g of octane. The molar mass of octane is 114.33 g mol^-1. 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O Δ_rH°= -11018 kJ

Using the following equation for the combustion of octane, calculate the amount of moles of carbon dioxide formed from 100.0 g of octane. The molar mass of octane is 114.33 g mol^-1. The molar mass of carbon dioxide is 44.0095 g mol^-1. 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O Δ_rH°= -11018 kJ

Choose the reaction that illustrates Δ_fH° for Ca(NO₃)₂.

Calculate the internal energy change, Δ_rU, for the combustion of 29.3 g of vitamin C (C₆H₈O₆, molar mass = 176.124 g mol^-1)if the combustion inside a bomb calorimeter, C_cal = 8.31 kJ °C^-1, causes a temperature change from 21.5 °C to 68.3 °C.

Calculate the heat transfer, in J, when 5.00 g of chromium (specific heat capacity = 0.449 J g^-1 °C^-1)at 0.00 °C is placed in 50.0 mL of water. The final temperature of the water is 23.8 °C. The chromium is defined as the system in this scenario.

A chemist wishes to calibrate a bomb calorimeter, so she combusts 5.58 g of 4-pentenoic acid, Δ_combustionU = -26.77 kJ g^-1, which causes a temperature change from 23.4 °C to 38.9 °C. What should the chemist report for the value of C_cal?

Use the standard reaction enthalpies given below to determine Δ_rH° for the following reaction: 2S(s)+ 3O₂(g)→ 2SO₃(g) Δ_rH°= ? Given: SO₂(g)→ S(s)+ O₂(g) Δ_rH°= +296.8 kJ 2SO₂(g)+ O₂(g)→ 2SO₃(g)Δ_rH°= -197.8 kJ

Using the following thermochemical equation, determine the amount of heat produced from the combustion of 24.3 g benzene (C₆H₆). The molar mass of benzene is 78.11 g mol^-1 2C₆H₆(l)+ 15O₂(g)→ 12CO₂(g)+ 6H₂O(g)Δ_rH°= -6278 kJ

Calculate the internal energy change, Δ_rU, for the combustion of 6.9261 g of diethylene glycol (C₄H₁₀O₃, molar mass = 106.120 g mol^-1)if the combustion inside a bomb calorimeter, C_cal = 13.84 kJ °C^-1, causes a temperature change from 22.8 °C to 34.0 °C.

The specific heat capacity of solid copper metal is 0.385 J g^-1 K^-1. How many joules of heat are needed to raise the temperature of a 1.55 kg block of copper from 33.0 °C to 77.5 °C?