Question 1

Which of the following processes is exothermic?

Accepted Answer

A)  the ionization of a lithium atom 
B)  the breaking of a Cl-Cl bond 
C)  the sublimation of dry ice (CO2(s)) 
D)  the reaction associated with   H° for an ionic compound 
A)  the ionization of a lithium atom 
B)  the breaking of a Cl-Cl bond 
C)  the sublimation of dry ice (CO2(s)) 
D)  the reaction associated with   H° for an ionic compound

Question 2

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   . 2C8H18 + 25O2 → 16CO2 + 18H2O   H° = -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 3

According to the following thermochemical equation, what mass of H2O (in g) must form to produce 975 kJ of energy? SiO2(s) + 4HF(g) → SiF4(g) + 2H2O(l)   H° = -184 kJ

Accepted Answer

A)  68.0 g 
B)  102 g 
C)  54.1 g 
D)  191 g 
E)  95.5 g 
A)  68.0 g 
B)  102 g 
C)  54.1 g 
D)  191 g 
E)  95.5 g

Question 4

The change in enthalpy for any process occurring at constant pressure is equal to the ________.

Accepted Answer

A)  change in internal energy 
B)  heat at constant pressure 
C)  work done by the system 
D)  work done by the surroundings 
E)  internal energy plus the work done by the system 
A)  change in internal energy 
B)  heat at constant pressure 
C)  work done by the system 
D)  work done by the surroundings 
E)  internal energy plus the work done by the system

Question 5

10.618 g of an unknown salt is dissolved in a coffee cup calorimeter that contains 50.0 mL of water. The measured temperature decreased from 23.8 °C to 22.7 °C. Identify the unknown salt. The specific heat of water is 4.184 J g-1 °C-1, and assume the density of the solution is 1.00 g mL-1.

Accepted Answer

A)  NaF,   H = 0.91 kJ mol-1 
B)  NaBr,   H = -0.60 kJ mol-1 
C)  NaNO3,   H = 20.50 kJ mol-1 
D)  LiNO3,   H = -2.51 kJ mol-1 
E)  LiBr∙2H2O,   H = -23.26 kJ mol-1 
A)  NaF,   H = 0.91 kJ mol-1 
B)  NaBr,   H = -0.60 kJ mol-1 
C)  NaNO3,   H = 20.50 kJ mol-1 
D)  LiNO3,   H = -2.51 kJ mol-1 
E)  LiBr∙2H2O,   H = -23.26 kJ mol-1

Question 6

Hydrogen peroxide decomposes to water and oxygen at constant pressure by the following reaction:     (l) →   O(l) +   (g)   H = -196 kJ Calculate the value of q (kJ) in this exothermic reaction when 4.00 g of hydrogen peroxide decomposes at constant pressure?

Accepted Answer

A)  -0.0217 kJ   
B)  1.44 kJ   
C)  -2.31 ×   kJ   
D)  -23.1 kJ   
E)  -11.5 kJ   
A)  -0.0217 kJ   
B)  1.44 kJ   
C)  -2.31 ×   kJ   
D)  -23.1 kJ   
E)  -11.5 kJ

Question 7

Identify a substance that is not in its standard state.

Accepted Answer

A)  CO(s) 
B)  Ba(s) 
C)  H2(g) 
D)  O2(g) 
E)  Ni(s) 
A)  CO(s) 
B)  Ba(s) 
C)  H2(g) 
D)  O2(g) 
E)  Ni(s)

Question 8

The standard state of sulfur is ________.

Accepted Answer

The answer of The standard state of sulfur is ________....

Question 9

Using the following equation for the combustion of octane, calculate the amount of moles of oxygen that reacts with 100.0 g of octane. The molar mass of octane is 114.33 g   . The molar mass of carbon dioxide is 44.0095 g   . 2C8H18 + 25O2 → 16CO2 + 18H2O   H° = -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) energy flows out of the system into the surroundings 
B) energy flows into the system from the surroundings 
C) work done by the system on the surroundings 
D) the system loses thermal energy to the surroundings 
E) the system gains thermal energy from the surroundings
F)work done on the system by the surroundings 
A) energy flows out of the system into the surroundings 
B) energy flows into the system from the surroundings 
C) work done by the system on the surroundings 
D) the system loses thermal energy to the surroundings 
E) the system gains thermal energy from the surroundings
F)work done on the system by the surroundings

Question 11

How much energy is required to decompose 765 g of PCl3 according to the reaction below? The molar mass of PCl3 is 137.32 g   and may be useful. 4PCl3(g) → P4(s) + 6Cl2(g)   H° = +1207 kJ

Accepted Answer

A)  2.31 × 103 kJ 
B)  4.33 × 103 kJ 
C)  6.72 × 103 kJ 
D)  1.68 × 103 kJ 
E)  5.95 × 103 kJ 
A)  2.31 × 103 kJ 
B)  4.33 × 103 kJ 
C)  6.72 × 103 kJ 
D)  1.68 × 103 kJ 
E)  5.95 × 103 kJ

Question 12

A 4.98 g sample of aniline (C6H5NH2, molar mass = 93.13 g   ) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ   . If the temperature rose from 29.5 °C to 69.8 °C, determine the value of   U for the combustion of aniline.

Accepted Answer

A)  +7.81 × 103 kJ mol-1 
B)  -3.20 × 103 kJ mol-1 
C)  +1.71 × 103 kJ mol-1 
D)  -1.71 × 103 kJ mol-1 
E)  -7.81 × 103 kJ mol-1 
A)  +7.81 × 103 kJ mol-1 
B)  -3.20 × 103 kJ mol-1 
C)  +1.71 × 103 kJ mol-1 
D)  -1.71 × 103 kJ mol-1 
E)  -7.81 × 103 kJ mol-1

Question 13

Calculate the internal energy change, ΔrU, for the combustion of 9.467 g of L-alanine (C3H7NO2, molar mass = 89.094 g mol-1) if the combustion inside a bomb calorimeter, Ccal = 7.83 kJ °C-1, causes a temperature change from 24.7 °C to 46.1 °C.

Accepted Answer

A)  -1.58 × 103 kJ mol-1 
B)  6.14 × 103 kJ mol-1 
C)  -3.48 × 103 kJ mol-1 
D)  -8.60 × 102 kJ mol-1 
E)  3.84 × 103 kJ mol-1 
A)  -1.58 × 103 kJ mol-1 
B)  6.14 × 103 kJ mol-1 
C)  -3.48 × 103 kJ mol-1 
D)  -8.60 × 102 kJ mol-1 
E)  3.84 × 103 kJ mol-1

Question 14

Identify what a coffee cup 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 15

A bomb calorimeter with a heat capacity of 13.9 kJ °C-1 has an initial temperature of 21.9 °C. If 5.00 g of propanal (C3H6O, molar mass = 58.0791 g mol-1, ΔrU = -1822.7 kJ mol-1 for combustion) is combusted, calculate the final temperature of the calorimeter.

Accepted Answer

A)  26.1 °C 
B)  16.7 °C 
C)  33.2 °C 
D)  43.1 °C 
E)  34.0 °C 
A)  26.1 °C 
B)  16.7 °C 
C)  33.2 °C 
D)  43.1 °C 
E)  34.0 °C

Question 16

Choose the reaction that illustrates ΔH° 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 17

A 6.55 g sample of aniline (C6H5NH2, molar mass = 93.13 g   ) was combusted in a bomb calorimeter. If the temperature rose by 32.9 °C, use the information below to determine the heat capacity of the calorimeter. 4C6H5NH2(l) + 35O2(g) → 24CO2(g) + 14H2O(g) + 4NO2(g)
ΔrU= -3.20 × 103 kJ mol-1

Accepted Answer

A)  97.3 kJ   
B)  38.9 kJ   
C)  5.94 kJ   
D)  6.84 kJ   
E)  12.8 kJ   
A)  97.3 kJ   
B)  38.9 kJ   
C)  5.94 kJ   
D)  6.84 kJ   
E)  12.8 kJ

Question 18

The specific heat capacity of methane gas is 2.20 J     . How many joules of heat are needed to raise the temperature of 5.00 g of methane from 36.0 °C to 75.0 °C?

Accepted Answer

A)  17.2 J 
B)  0.0113 J 
C)  88.6 J 
D)  1.22 × 103 J 
E)  429 J 
A)  17.2 J 
B)  0.0113 J 
C)  88.6 J 
D)  1.22 × 103 J 
E)  429 J

Question 19

The combustion of titanium with oxygen produces titanium dioxide: Ti(s) +   (g) →   (s)
When 2.090 g of titanium is combusted in a bomb calorimeter, the temperature of the calorimeter increases from 25.00 °C to 91.30 °C. In a separate experiment, the heat capacity of the calorimeter is measured to be 9.84 kJ   . The heat of reaction for the combustion of a mole of Ti in this calorimeter is ________ kJ   .

Accepted Answer

A)  14.9 
B)  652 
C)  -3.40 
D)  -28.5 
E)  -1.49 ×   
A)  14.9 
B)  652 
C)  -3.40 
D)  -28.5 
E)  -1.49 ×

Question 20

Use the   H° information provided to calculate   H° for the following: SO2Cl2 (g) + 2H2O(l)→ 2HCl(g) + H2SO4(l) ΔrH° = ?   H° (kJ   ) 
SO2Cl2(g) -364
H2O(l) -286
HCl(g) 92
H2SO4(l) -814

Accepted Answer

A)  -256 kJ mol-1 
B)  +161 kJ mol-1 
C)  -62 kJ mol-1 
D)  +800. kJ mol-1 
E)  -422 kJ mol-1 
A)  -256 kJ mol-1 
B)  +161 kJ mol-1 
C)  -62 kJ mol-1 
D)  +800. kJ mol-1 
E)  -422 kJ mol-1

Exam 6: Thermochemistry

Which of the following processes is exothermic?

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 . 2C8H18 + 25O2 → 16CO2 + 18H2O H° = -11018 kJ

According to the following thermochemical equation, what mass of H2O (in g) must form to produce 975 kJ of energy? SiO2(s) + 4HF(g) → SiF4(g) + 2H2O(l) H° = -184 kJ

The change in enthalpy for any process occurring at constant pressure is equal to the ________.

10.618 g of an unknown salt is dissolved in a coffee cup calorimeter that contains 50.0 mL of water. The measured temperature decreased from 23.8 °C to 22.7 °C. Identify the unknown salt. The specific heat of water is 4.184 J g-1 °C-1, and assume the density of the solution is 1.00 g mL-1.

Hydrogen peroxide decomposes to water and oxygen at constant pressure by the following reaction: (l) → O(l) + (g) H = -196 kJ Calculate the value of q (kJ) in this exothermic reaction when 4.00 g of hydrogen peroxide decomposes at constant pressure?

Identify a substance that is not in its standard state.

The standard state of sulfur is ________.

Using the following equation for the combustion of octane, calculate the amount of moles of oxygen that reacts with 100.0 g of octane. The molar mass of octane is 114.33 g . The molar mass of carbon dioxide is 44.0095 g . 2C8H18 + 25O2 → 16CO2 + 18H2O H° = -11018 kJ

Match the following. --q

How much energy is required to decompose 765 g of PCl3 according to the reaction below? The molar mass of PCl3 is 137.32 g and may be useful. 4PCl3(g) → P4(s) + 6Cl2(g) H° = +1207 kJ

A 4.98 g sample of aniline (C6H5NH2, molar mass = 93.13 g ) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ . If the temperature rose from 29.5 °C to 69.8 °C, determine the value of U for the combustion of aniline.

Calculate the internal energy change, ΔrU, for the combustion of 9.467 g of L-alanine (C3H7NO2, molar mass = 89.094 g mol-1) if the combustion inside a bomb calorimeter, Ccal = 7.83 kJ °C-1, causes a temperature change from 24.7 °C to 46.1 °C.

Identify what a coffee cup calorimeter measures.

A bomb calorimeter with a heat capacity of 13.9 kJ °C-1 has an initial temperature of 21.9 °C. If 5.00 g of propanal (C3H6O, molar mass = 58.0791 g mol-1, ΔrU = -1822.7 kJ mol-1 for combustion) is combusted, calculate the final temperature of the calorimeter.

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

A 6.55 g sample of aniline (C6H5NH2, molar mass = 93.13 g ) was combusted in a bomb calorimeter. If the temperature rose by 32.9 °C, use the information below to determine the heat capacity of the calorimeter. 4C6H5NH2(l) + 35O2(g) → 24CO2(g) + 14H2O(g) + 4NO2(g) ΔrU= -3.20 × 103 kJ mol-1

The specific heat capacity of methane gas is 2.20 J . How many joules of heat are needed to raise the temperature of 5.00 g of methane from 36.0 °C to 75.0 °C?

Use the H° information provided to calculate H° for the following: SO2Cl2 (g) + 2H2O(l)→ 2HCl(g) + H2SO4(l) ΔrH° = ? H° (kJ ) SO2Cl2(g) -364 H2O(l) -286 HCl(g) 92 H2SO4(l) -814

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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 . 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O H°= -11018 kJ

According to the following thermochemical equation, what mass of H₂O (in g) must form to produce 975 kJ of energy? SiO₂(s) + 4HF(g) → SiF₄(g) + 2H₂O(l) H°= -184 kJ

10.618 g of an unknown salt is dissolved in a coffee cup calorimeter that contains 50.0 mL of water. The measured temperature decreased from 23.8 °C to 22.7 °C. Identify the unknown salt. The specific heat of water is 4.184 J g^-1 °C^-1, and assume the density of the solution is 1.00 g mL^-1.

Using the following equation for the combustion of octane, calculate the amount of moles of oxygen that reacts with 100.0 g of octane. The molar mass of octane is 114.33 g . The molar mass of carbon dioxide is 44.0095 g . 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O H°= -11018 kJ

How much energy is required to decompose 765 g of PCl₃ according to the reaction below? The molar mass of PCl₃ is 137.32 g and may be useful. 4PCl₃(g) → P₄(s) + 6Cl₂(g) H° = +1207 kJ

A 4.98 g sample of aniline (C₆H₅NH₂, molar mass = 93.13 g ) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ . If the temperature rose from 29.5 °C to 69.8 °C, determine the value of U for the combustion of aniline.

Calculate the internal energy change, Δ_rU, for the combustion of 9.467 g of L-alanine (C₃H₇NO₂, molar mass = 89.094 g mol^-1) if the combustion inside a bomb calorimeter, C_cal = 7.83 kJ °C^-1, causes a temperature change from 24.7 °C to 46.1 °C.

A bomb calorimeter with a heat capacity of 13.9 kJ °C^-1 has an initial temperature of 21.9 °C. If 5.00 g of propanal (C₃H₆O, molar mass = 58.0791 g mol^-1, Δ_rU = -1822.7 kJ mol^-1 for combustion) is combusted, calculate the final temperature of the calorimeter.

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

Use the H° information provided to calculate H° for the following: SO₂Cl₂ (g) + 2H₂O(l)→ 2HCl(g) + H₂SO4(l) Δ_rH°= ? H°(kJ ) SO₂Cl₂(g) -364 H₂O(l) -286 HCl(g) 92 H₂SO₄(l) -814