Question 1

Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter. The reaction causes the temperature of the resulting solution to fall below room temperature. Which of the following statements is TRUE?

Accepted Answer

A)  The products have a lower potential energy than the reactants. 
B)  This type of experiment will provide data to calculate  U. 
C)  The reaction is exothermic. 
D)  Energy is leaving the system during the reaction. 
E)  None of the above statements is true.

Question 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.

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

Question 3

How much heat is absorbed/released when 40.00 g of NH3(g) reacts in the presence of excess  (g) to produce NO(g) and H2O(l) according to the following chemical equation? 
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l)  H° = 1168 kJ

Accepted Answer

A)  685.8 kJ of heat are absorbed. 
B)  685.8 kJ of heat are released. 
C)  2743 kJ of heat are absorbed. 
D)  2743 kJ of heat are released.

Question 4

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  . 2C6H6(l) + 15O2(g) → 12CO2(g) + 6H2O(g)  H° = -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

Question 5

Use the  H° and  H° information provided to calculate  H° for SO3(g):  H° (kJ  ) 2SO2(g) + O2(g) → 2SO3(g)  H° = -198 kJ SO2(g) -297

Accepted Answer

A)  -792 kJ mol-1 
B)  -248 kJ mol-1 
C)  -495 kJ mol-1 
D)  -578 kJ mol-1 
E)  -396 kJ mol-1

Question 6

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

Question 7

Calculate the amount of heat (in kJ) necessary to raise the temperature of 47.8 g benzene by 57.0 K. The specific heat capacity of benzene is 1.05 J g-1 °C-1.

Accepted Answer

A)  1.61 kJ 
B)  16.6 kJ 
C)  2.59 kJ 
D)  2.86 kJ 
E)  3.85 kJ

Question 8

Which of the following signs on q and w represent a system that is doing work on the surroundings as well as gaining heat from the surroundings?

Accepted Answer

A)  q = +, w = - 
B)  q = -, w = + 
C)  q = +, w = + 
D)  q = -, w = - 
E)  None of these represent the system referenced above.

Question 9

Calculate the amount (mass) of acetaldehyde (C2H4O, molar mass = 44.0526 g mol-1) that causes a bomb calorimeter with a heat capacity of 12.91 kJ °C-1 to have a temperature increase from 27.8 °C to 41.7 °C. The ΔrU for the combustion of acetaldehyde is -1166.9 kJ mol-1.

Accepted Answer

A)  6.77 g 
B)  8.67 g 
C)  4.29 g 
D)  7.30 g 
E)  5.55 g

Question 10

9.26 g of an unknown solid is dissolved in a coffee cup calorimeter that contains 62.0 mL of water. The measured temperature increased from 23.4 °C to 24.7 °C. 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. Calculate the molecular weight of the unknown solid if the  H was determined to be -2.51 kJ mol-1 via another experiment.

Accepted Answer

A)  69 g mol-1 
B)  48 g mol-1 
C)  76 g mol-1 
D)  184 g mol-1 
E)  93 g mol-1

Question 11

The standard state of carbon is ________.

Accepted Answer

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

Question 12

A piece of gold with a mass of 21.0 g was heated to 100.0 °C and placed inside a coffee cup calorimeter. The temperature of the water inside the calorimeter increased from 23.8 °C to 25.5 °C. The specific heat capacity of water is 4.184 J g-1 °C-1 and the specific heat capacity of gold is 0.129 J g-1 °C-1. Calculate the mass of water contained inside the calorimeter.

Accepted Answer

A)  28.4 g 
B)  16.0 g 
C)  21.0 g 
D)  39.5 g 
E)  32.9 g

Question 13

Calculate the mass of sodium cyanate (NaOCN, molar mass = 65.0066 g mol-1) required to lower the temperature from 24.1 °C to 23.0 °C in a coffee cup calorimeter containing 98 mL of water. The enthalpy of solution for NaOCN is 19.20 kJ mol-1. 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)  0.75 g 
B)  1.1 g 
C)  3.8 g 
D)  1.5 g 
E)  4.8 g

Question 14

For  U to always be -, what must be true?

Accepted Answer

A)  q = w 
B)  +q > -w 
C)  +w > -q 
D)  -w > +q

Question 15

Identify the unit of heat capacity.

Accepted Answer

A)  J °C-1 
B)  J g-1 °C-1 
C)  J mol-1 °C-1 
D)  g °C-1 
E)  mol °C-1

Question 16

Match the following.
-energy associated with the position of an object

Accepted Answer

A) thermal energy 
B) chemical energy 
C) kinetic energy 
D) potential energy

Question 17

Use the standard reaction enthalpies given below to determine  H° for the following reaction: 2NO(g) + O2(g) → 2NO2(g)  H° = ?
Given:
N2(g) + O2(g) → 2NO(g)  H° = +183 kJ
1/2 N2(g) + O2(g) → NO2(g)  H° = +33 kJ

Accepted Answer

A)  -150. kJ mol-1 
B)  -117 kJ mol-1 
C)  -333 kJ mol-1 
D)  +115 kJ mol-1 
E)  +238 kJ mol-1

Question 18

Use the standard reaction enthalpies given below to determine  H° for the following reaction: P4(g) + 10Cl2(g) → 4PCl5(s)  H° = ?
Given:
PCl5(s) → PCl3(g) + Cl2(g)  H°= +157 kJ
P4(g) + 6Cl2(g) → 4PCl3(g)  H° = -1207 kJ

Accepted Answer

A)  -1835 kJ mol-1 
B)  -1364 kJ mol-1 
C)  -1050 kJ mol-1 
D)  -1786 kJ mol-1 
E)  -2100 kJ mol-1

Question 19

Define molar heat capacity.

Accepted Answer

A)  the quantity of heat required to raise the temperature of 1 mol of a substance by 1 °C 
B)  the quantity of heat required to change a system's temperature by 1 °C 
C)  the quantity of heat required to raise the temperature of 1 g of a substance by 1 °C 
D)  the quantity of heat required to raise the temperature of 1 g of a substance by 1 °F 
E)  the quantity of heat required to raise the temperature of 1 L of a substance by 1 °C

Question 20

Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K. The specific heat capacity of ethanol is 2.42 J g-1 °C-1.

Accepted Answer

A)  57.0 kJ 
B)  16.6 kJ 
C)  73.6 kJ 
D)  28.4 kJ 
E)  12.9 kJ

Exam 6: Thermochemistry

Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter. The reaction causes the temperature of the resulting solution to fall below room temperature. Which of the following statements is TRUE?

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.

How much heat is absorbed/released when 40.00 g of NH₃(g) reacts in the presence of excess (g) to produce NO(g) and H₂O(l) according to the following chemical equation? 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(l) H° = 1168 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 . 2C₆H₆(l) + 15O₂(g) → 12CO₂(g) + 6H₂O(g) H°= -6278 kJ

Use the H° and H°information provided to calculate H° for SO₃(g) : H°(kJ ) 2SO₂(g) + O₂(g) → 2SO₃(g) H°= -198 kJ SO₂(g) -297

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.

Calculate the amount of heat (in kJ) necessary to raise the temperature of 47.8 g benzene by 57.0 K. The specific heat capacity of benzene is 1.05 J g^-1 °C^-1.

Which of the following signs on q and w represent a system that is doing work on the surroundings as well as gaining heat from the surroundings?

Calculate the amount (mass) of acetaldehyde (C₂H₄O, molar mass = 44.0526 g mol^-¹) that causes a bomb calorimeter with a heat capacity of 12.91 kJ °C^-1 to have a temperature increase from 27.8 °C to 41.7 °C. The Δ_rU for the combustion of acetaldehyde is -1166.9 kJ mol^-1.

The standard state of carbon is ________.

For U to always be -, what must be true?

Identify the unit of heat capacity.

Match the following. -energy associated with the position of an object

Use the standard reaction enthalpies given below to determine H° for the following reaction: 2NO(g) + O₂(g) → 2NO₂(g) H°= ? Given: N₂(g) + O₂(g) → 2NO(g) H°= +183 kJ 1/2 N₂(g) + O₂(g) → NO₂(g) H°= +33 kJ

Use the standard reaction enthalpies given below to determine H° for the following reaction: P₄(g) + 10Cl₂(g) → 4PCl₅(s) H°= ? Given: PCl₅(s) → PCl₃(g) + Cl₂(g) H°= +157 kJ P₄(g) + 6Cl₂(g) → 4PCl₃(g) H° = -1207 kJ

Define molar heat capacity.

Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K. The specific heat capacity of ethanol is 2.42 J g^-1 °C^-1.

Exam 6: Thermochemistry

Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter. The reaction causes the temperature of the resulting solution to fall below room temperature. Which of the following statements is TRUE?

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.

How much heat is absorbed/released when 40.00 g of NH3(g) reacts in the presence of excess (g) to produce NO(g) and H2O(l) according to the following chemical equation? 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l) H° = 1168 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 . 2C6H6(l) + 15O2(g) → 12CO2(g) + 6H2O(g) H° = -6278 kJ

Use the H° and H° information provided to calculate H° for SO3(g) : H° (kJ ) 2SO2(g) + O2(g) → 2SO3(g) H° = -198 kJ SO2(g) -297

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.

Calculate the amount of heat (in kJ) necessary to raise the temperature of 47.8 g benzene by 57.0 K. The specific heat capacity of benzene is 1.05 J g-1 °C-1.

Which of the following signs on q and w represent a system that is doing work on the surroundings as well as gaining heat from the surroundings?

Calculate the amount (mass) of acetaldehyde (C2H4O, molar mass = 44.0526 g mol-1) that causes a bomb calorimeter with a heat capacity of 12.91 kJ °C-1 to have a temperature increase from 27.8 °C to 41.7 °C. The ΔrU for the combustion of acetaldehyde is -1166.9 kJ mol-1.

The standard state of carbon is ________.

For U to always be -, what must be true?

Identify the unit of heat capacity.

Match the following. -energy associated with the position of an object

Use the standard reaction enthalpies given below to determine H° for the following reaction: 2NO(g) + O2(g) → 2NO2(g) H° = ? Given: N2(g) + O2(g) → 2NO(g) H° = +183 kJ 1/2 N2(g) + O2(g) → NO2(g) H° = +33 kJ

Use the standard reaction enthalpies given below to determine H° for the following reaction: P4(g) + 10Cl2(g) → 4PCl5(s) H° = ? Given: PCl5(s) → PCl3(g) + Cl2(g) H°= +157 kJ P4(g) + 6Cl2(g) → 4PCl3(g) H° = -1207 kJ

Define molar heat capacity.

Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K. The specific heat capacity of ethanol is 2.42 J g-1 °C-1.

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.

How much heat is absorbed/released when 40.00 g of NH₃(g) reacts in the presence of excess (g) to produce NO(g) and H₂O(l) according to the following chemical equation? 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(l) H° = 1168 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 . 2C₆H₆(l) + 15O₂(g) → 12CO₂(g) + 6H₂O(g) H°= -6278 kJ

Use the H° and H°information provided to calculate H° for SO₃(g) : H°(kJ ) 2SO₂(g) + O₂(g) → 2SO₃(g) H°= -198 kJ SO₂(g) -297

Calculate the amount of heat (in kJ) necessary to raise the temperature of 47.8 g benzene by 57.0 K. The specific heat capacity of benzene is 1.05 J g^-1 °C^-1.

Calculate the amount (mass) of acetaldehyde (C₂H₄O, molar mass = 44.0526 g mol^-¹) that causes a bomb calorimeter with a heat capacity of 12.91 kJ °C^-1 to have a temperature increase from 27.8 °C to 41.7 °C. The Δ_rU for the combustion of acetaldehyde is -1166.9 kJ mol^-1.

Use the standard reaction enthalpies given below to determine H° for the following reaction: 2NO(g) + O₂(g) → 2NO₂(g) H°= ? Given: N₂(g) + O₂(g) → 2NO(g) H°= +183 kJ 1/2 N₂(g) + O₂(g) → NO₂(g) H°= +33 kJ

Use the standard reaction enthalpies given below to determine H° for the following reaction: P₄(g) + 10Cl₂(g) → 4PCl₅(s) H°= ? Given: PCl₅(s) → PCl₃(g) + Cl₂(g) H°= +157 kJ P₄(g) + 6Cl₂(g) → 4PCl₃(g) H° = -1207 kJ

Calculate the amount of heat (in kJ) required to raise the temperature of a 79.0 g sample of ethanol from 298.0 K to 385.0 K. The specific heat capacity of ethanol is 2.42 J g^-1 °C^-1.