Question 1

How many joules are in 1.20 ×103 calories? (1 cal = 4.184 J)

Accepted Answer

A)  8.33 × 10-4 J 
B)  3.49 × 10-3 J 
C)  2.39 × 10-1 J 
D)  2.86 × 102 J 
E)  5.02 × 103 J 
A)  8.33 × 10-4 J 
B)  3.49 × 10-3 J 
C)  2.39 × 10-1 J 
D)  2.86 × 102 J 
E)  5.02 × 103 J E

Question 2

a. Explain fully what is meant by the term "state function."
b. (i) Give two examples of thermodynamic quantities which are state functions.
(ii) Give two examples of thermodynamic quantities which are not state functions.

Accepted Answer

a. A state function depends only on the initial and final states, not on its history or the path followed in a process.
b. (i) internal energy, enthalpy (and possibly T, P, etc.)
(ii) heat and work

Question 3

Suppose a 50-g block of silver (specific heat = 0.2350 J/g·°C) at 100°C is placed in contact with a 50-g block of iron (specific heat = 0.4494 J/g·°C) at 0°C, and the two blocks are insulated from the rest of the universe. The final temperature of the two blocks

Accepted Answer

A)  will be higher than 50°C. 
B)  will be lower than 50°C. 
C)  will be exactly 50°C. 
D)  is unrelated to the composition of the blocks. 
E)  cannot be predicted. 
A)  will be higher than 50°C. 
B)  will be lower than 50°C. 
C)  will be exactly 50°C. 
D)  is unrelated to the composition of the blocks. 
E)  cannot be predicted. B

Question 4

The enthalpy of vaporization of a compound is always positive.

Accepted Answer

A) True 
 B)False

Question 5

Using Hess's law, what is the standard enthalpy of formation, ΔH°f of manganese(II) oxide, MnO(s)?

Accepted Answer

A)  -520.9 kJ/mol 
B)  -396.5 kJ/mol 
C)  -384.9 kJ/mol 
D)  -147.6 kJ/mol 
E)  24 kJ/mol 
A)  -520.9 kJ/mol 
B)  -396.5 kJ/mol 
C)  -384.9 kJ/mol 
D)  -147.6 kJ/mol 
E)  24 kJ/mol

Question 6

A system which does work on the surroundings with no heat change has

Accepted Answer

A) w 0, ΔU > 0. C) w > 0, ΔU 0. E) w < 0, ΔU < 0. A) w 0, ΔU > 0. C) w > 0, ΔU 0. E) w < 0, ΔU < 0.

Question 7

The enthalpy of combustion of acetylene (C2H2) is described by
C2H2(g) + 5/2O2(g) → 2CO2(g) + H2O(l) ΔH°rxn= -1299 kJ/mol
Calculate the enthalpy of formation of acetylene, given the following enthalpies of formation: ΔH°f(CO2(g)) = -393.5 kJ/mol; ΔH°f(H2O(l)) = -285.8 kJ/mol

Accepted Answer

Question 8

Complete the sentence: When heat is transferred to the system, the process is said to be ________, and the sign of q is ________.

Accepted Answer

A)  exothermic, positive 
B)  exothermic, negative 
C)  endothermic, positive 
D)  endothermic, negative 
E)  forbidden, indeterminate 
A)  exothermic, positive 
B)  exothermic, negative 
C)  endothermic, positive 
D)  endothermic, negative 
E)  forbidden, indeterminate

Question 9

The sign of q when heat is released by the system is ________.

Accepted Answer

The answer of The sign of q when heat is...

Question 10

Natural gas, or methane, is an important fuel. Combustion of one mole of methane releases 802.3 kJ of energy. How much energy does that represent in kcal? (1 cal = 4.184 J)

Accepted Answer

A)  1.92 × 10-1 kcal 
B)  1.92 × 102 kcal 
C)  3.36 × 103 kcal 
D)  1.92 × 105 kcal 
E)  3.36 × 106 kcal 
A)  1.92 × 10-1 kcal 
B)  1.92 × 102 kcal 
C)  3.36 × 103 kcal 
D)  1.92 × 105 kcal 
E)  3.36 × 106 kcal

Question 11

The heat of solution of ammonium nitrate is 26.2 kJ/mol. If a 5.368 g sample of NH4NO3 is added to 40.0 mL of water in a calorimeter at 23.5°C, what is the final temperature of the solution? The specific heat of water is 4.18 J/g·°C and the heat capacity of the calorimeter is 0.650 kJ/°C.

Accepted Answer

A)  14.3°C 
B)  20.8°C 
C)  -7.7°C 
D)  25.6°C 
E)  21.4°C 
A)  14.3°C 
B)  20.8°C 
C)  -7.7°C 
D)  25.6°C 
E)  21.4°C

Question 12

Benzene is a starting material in the synthesis of nylon fibers and polystyrene (Styrofoam). Its specific heat capacity is 1.74 J/g·°C. If 16.7 kJ of energy is absorbed by a 225-g sample of benzene at 20.0°C, what is its final temperature?

Accepted Answer

A)  -22.7°C 
B)  37.7°C 
C)  42.7°C 
D)  62.7°C 
E)  80.1°C 
A)  -22.7°C 
B)  37.7°C 
C)  42.7°C 
D)  62.7°C 
E)  80.1°C

Question 13

The specific heat of gold is 0.129 J/g·°C. What is the molar heat capacity of gold?

Accepted Answer

A)  0.0394 J/mol·°C 
B)  0.129 J/mol·°C 
C)  25.4 J/mol·°C 
D)  39.4 kJ/mol·°C 
E)  197 J/mol·°C 
A)  0.0394 J/mol·°C 
B)  0.129 J/mol·°C 
C)  25.4 J/mol·°C 
D)  39.4 kJ/mol·°C 
E)  197 J/mol·°C

Question 14

What is the change in internal energy in joules for a system that releases 154 J of heat and does 125 J of work on its surroundings?

Accepted Answer

A)  -29 J 
B)  279 J 
C)  29 J 
D)  1.23 J 
E)  -279 J 
A)  -29 J 
B)  279 J 
C)  29 J 
D)  1.23 J 
E)  -279 J

Question 15

Glycine, C2H5O2N, is important for biological energy. The combustion reaction of glycine is described by the following thermochemical equation. 4C2H5O2N(s) + 9O2(g) → 8CO2(g) + 10H2O(l) + 2N2(g) ΔH°rxn = -3896 kJ/mol
What is the standard enthalpy of formation of solid glycine?

Accepted Answer

A)  -51.90 kJ/mol 
B)  -527.5 kJ/mol 
C)  -974.0 kJ/mol 
D)  -1502 kJ/mol 
E)  -2476 kJ/mol 
A)  -51.90 kJ/mol 
B)  -527.5 kJ/mol 
C)  -974.0 kJ/mol 
D)  -1502 kJ/mol 
E)  -2476 kJ/mol

Question 16

A common laboratory reaction is the neutralization of an acid with a base. When 50.0 mL of 0.500 M HCl at 25.0°C is added to 50.0 mL of 0.500 M NaOH at 25.0°C in a coffee cup calorimeter, the temperature of the mixture rises to 28.2°C. What is the heat of reaction per mole of acid? Assume the mixture has a specific heat capacity of 4.18 J/g·°C and that the densities of the reactant solutions are both 1.00 g/mL.

Accepted Answer

A)  670 J 
B)  1300 J 
C)  27 kJ 
D)  54 kJ 
E)  > 100 kJ 
A)  670 J 
B)  1300 J 
C)  27 kJ 
D)  54 kJ 
E)  > 100 kJ

Question 17

The dissolution of barium hydroxide in water is an exothermic process. Which statement is correct?

Accepted Answer

A)  The enthalpy of solid barium hydroxide plus pure water is less than that of the solution, at the same temperature. 
B)  The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution, at the same temperature. 
C)  The enthalpy of solid barium hydroxide plus pure water is the same as that of the solution, at the same temperature. 
D)  The temperature of the solution is lower than of the barium hydroxide and water before mixing. 
E)  When barium hydroxide dissolves in water, the system does work on the surroundings. 
A)  The enthalpy of solid barium hydroxide plus pure water is less than that of the solution, at the same temperature. 
B)  The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution, at the same temperature. 
C)  The enthalpy of solid barium hydroxide plus pure water is the same as that of the solution, at the same temperature. 
D)  The temperature of the solution is lower than of the barium hydroxide and water before mixing. 
E)  When barium hydroxide dissolves in water, the system does work on the surroundings.

Question 18

When Karl Kaveman adds chilled grog to his new granite mug, he removes 10.9 kJ of energy from the mug. If it has a mass of 625 g and was at 25°C, what is its new temperature? Specific heat capacity of granite = 0.79 J/g·°C.

Accepted Answer

A)  3°C 
B)  14°C 
C)  22°C 
D)  47°C 
E)  None of these choices is correct. 
A)  3°C 
B)  14°C 
C)  22°C 
D)  47°C 
E)  None of these choices is correct.

Question 19

All elements in their standard state have an enthalpy of formation equal to zero.

Accepted Answer

A) True 
 B)False

Question 20

How many calories are in 854.3 J? (1 cal = 4.184 J)

Accepted Answer

A)  4.897 × 10-3 cal 
B)  204.2 cal 
C)  1.171 ×10-3 cal 
D)  0.2390 cal 
E)  3574 cal 
A)  4.897 × 10-3 cal 
B)  204.2 cal 
C)  1.171 ×10-3 cal 
D)  0.2390 cal 
E)  3574 cal

Exam 5: Thermochemistry

How many joules are in 1.20 ×103 calories? (1 cal = 4.184 J)

a. Explain fully what is meant by the term "state function." b. (i) Give two examples of thermodynamic quantities which are state functions. (ii) Give two examples of thermodynamic quantities which are not state functions.

Suppose a 50-g block of silver (specific heat = 0.2350 J/g·°C) at 100°C is placed in contact with a 50-g block of iron (specific heat = 0.4494 J/g·°C) at 0°C, and the two blocks are insulated from the rest of the universe. The final temperature of the two blocks

The enthalpy of vaporization of a compound is always positive.

Using Hess's law, what is the standard enthalpy of formation, ΔH°f of manganese(II) oxide, MnO(s)?

A system which does work on the surroundings with no heat change has

The enthalpy of combustion of acetylene (C2H2) is described by C2H2(g) + 5/2O2(g) → 2CO2(g) + H2O(l) ΔH°rxn= -1299 kJ/mol Calculate the enthalpy of formation of acetylene, given the following enthalpies of formation: ΔH°f(CO2(g)) = -393.5 kJ/mol; ΔH°f(H2O(l)) = -285.8 kJ/mol

Complete the sentence: When heat is transferred to the system, the process is said to be ________, and the sign of q is ________.

The sign of q when heat is released by the system is ________.

Natural gas, or methane, is an important fuel. Combustion of one mole of methane releases 802.3 kJ of energy. How much energy does that represent in kcal? (1 cal = 4.184 J)

The heat of solution of ammonium nitrate is 26.2 kJ/mol. If a 5.368 g sample of NH4NO3 is added to 40.0 mL of water in a calorimeter at 23.5°C, what is the final temperature of the solution? The specific heat of water is 4.18 J/g·°C and the heat capacity of the calorimeter is 0.650 kJ/°C.

Benzene is a starting material in the synthesis of nylon fibers and polystyrene (Styrofoam). Its specific heat capacity is 1.74 J/g·°C. If 16.7 kJ of energy is absorbed by a 225-g sample of benzene at 20.0°C, what is its final temperature?

The specific heat of gold is 0.129 J/g·°C. What is the molar heat capacity of gold?

What is the change in internal energy in joules for a system that releases 154 J of heat and does 125 J of work on its surroundings?

Glycine, C2H5O2N, is important for biological energy. The combustion reaction of glycine is described by the following thermochemical equation. 4C2H5O2N(s) + 9O2(g) → 8CO2(g) + 10H2O(l) + 2N2(g) ΔH°rxn = -3896 kJ/mol What is the standard enthalpy of formation of solid glycine?

The dissolution of barium hydroxide in water is an exothermic process. Which statement is correct?

When Karl Kaveman adds chilled grog to his new granite mug, he removes 10.9 kJ of energy from the mug. If it has a mass of 625 g and was at 25°C, what is its new temperature? Specific heat capacity of granite = 0.79 J/g·°C.

All elements in their standard state have an enthalpy of formation equal to zero.

How many calories are in 854.3 J? (1 cal = 4.184 J)

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How many joules are in 1.20 ×10³ calories? (1 cal = 4.184 J)

Using Hess's law, what is the standard enthalpy of formation, ΔH°_fof manganese(II) oxide, MnO(s)?

Complete the sentence: When heat is transferred to the system, the process is said to be , and the sign of q is .

The heat of solution of ammonium nitrate is 26.2 kJ/mol. If a 5.368 g sample of NH₄NO₃ is added to 40.0 mL of water in a calorimeter at 23.5°C, what is the final temperature of the solution? The specific heat of water is 4.18 J/g·°C and the heat capacity of the calorimeter is 0.650 kJ/°C.