CHEM 1040 Final Exam 2025| Actual Exam
Questions and Correct Answers
Question 1: Which of the following is an example of a non-spontaneous process?
A. Ice melting at room temperature
B. Sodium metal reacting violently with water
C. Rusting of iron at room temp
D. A ball rolling downhill
E. Water freezing at room temp
Correct Answer: E. Water freezing at room temp
Explanation: A non-spontaneous process requires external energy. At room temperature
(~25°C), water freezing (liquid to solid) is non-spontaneous as the freezing point of water is 0°C
at 1 atm, requiring cooling. Options A, B, C, and D are spontaneous under typical conditions.
Question 2: For the reaction: 2A + B₂ → 2AB, ΔH = +50.0 kJ
A. The reaction is endothermic
B. Heat is released to the surroundings
C. The standard enthalpy of formation for AB is 50.0 kJ
D. The bond energy for each A-B bond is 50.0 kJ
E. The molecule AB contains less energy than A or B₂
Correct Answer: A. The reaction is endothermic
Explanation: A positive ΔH (+50.0 kJ) indicates an endothermic reaction, absorbing heat
from the surroundings. Option B is incorrect (heat is absorbed). Options C, D, and E require
additional data (e.g., formation enthalpies or bond energies) not provided.
Question 3: An endothermic reaction causes the surroundings to:
A. Warm up
B. Become acidic
,C. Condense
D. Decrease in temp
E. Release CO₂
Correct Answer: D. Decrease in temp
Explanation: An endothermic reaction absorbs heat from the surroundings, causing the
surroundings to lose thermal energy and decrease in temperature. Other options are unrelated to
the thermal effects of an endothermic process.
Question 4: Which, if any, of the following processes is spontaneous under the specified
conditions?
A. H₂O(l) → H₂O(s) at 25°C, 1 atm
B. CO₂(s) → CO₂(g) at 0°C, 1 atm
C. 2H₂O(g) → 2H₂(g) + O₂(g) at 25°C, 1 atm
D. C(graphite) → C(diamond) at 25°C, 1 atm
E. None of these are spontaneous
Correct Answer: B. CO₂(s) → CO₂(g) at 0°C, 1 atm
Explanation: Sublimation of CO₂ (dry ice) is spontaneous at 0°C and 1 atm because its
sublimation point is around -78.5°C at 1 atm, and 0°C is well above this. Option A is non-
spontaneous (water freezes below 0°C). Options C and D have high activation energies or
unfavorable thermodynamics at standard conditions.
Question 5: Which is a statement of the second law of thermodynamics?
A. The energy of the universe is constant
B. The entropy of the universe is constant
C. The enthalpy of the universe is constant
D. The energy of the universe is decreasing
E. The entropy of the universe is increasing
Correct Answer: E. The entropy of the universe is increasing
,Explanation: The second law of thermodynamics states that the entropy of the universe
increases for spontaneous processes (ΔS_univ > 0). Option A relates to the first law (energy
conservation).
Question 6: What is ΔS for the reaction SO₃(g) + H₂O(l) → H₂SO₄(aq)?
A. 169.2 J/K
B. 343.2 J/K
C. -169.2 J/K
D. -29.4 J/K
E. 29.4 J/K
Correct Answer: C. -169.2 J/K
Explanation: Entropy decreases (negative ΔS) as the reaction combines a gas and liquid to
form a liquid, reducing molecular freedom. Using standard molar entropies (approximate values:
SO₃(g) ≈ 256 J/mol·K, H₂O(l) ≈ 70 J/mol·K, H₂SO₄(aq) ≈ 157 J/mol·K), ΔS = S_products -
S_reactants = 157 - (256 + 70) ≈ -169 J/K.
Question 7: For a particular process, 28 kJ of heat is absorbed and 15 kJ of work is done on the
surroundings. What is ΔU?
A. ΔU = +43 kJ
B. ΔU = -43 kJ
C. ΔU = -13 kJ
D. ΔU = +13 kJ
E. ΔU = +28 kJ
Correct Answer: D. ΔU = +13 kJ
Explanation: The first law of thermodynamics states ΔU = q + w. Heat absorbed (q = +28 kJ),
work done on surroundings (w = -15 kJ). Thus, ΔU = 28 - 15 = +13 kJ.
Question 8: Which is not a state function?
A. Internal energy
B. Volume
, C. Work
D. Pressure
E. Enthalpy
Correct Answer: C. Work
Explanation: State functions (e.g., internal energy, volume, pressure, enthalpy) depend only
on the current state, not the path. Work depends on the process path, making it a path function.
Question 9: A negative sign for ΔG indicates that, at constant T and P:
A. The reaction is exothermic
B. The reaction is endothermic
C. The reaction is fast
D. The reaction is spontaneous
E. ΔS of the system must be greater than 0
Correct Answer: D. The reaction is spontaneous
Explanation: A negative ΔG (ΔG < 0) indicates a spontaneous reaction at constant
temperature and pressure, per the Gibbs free energy equation (ΔG = ΔH - TΔS).
Question 10: Sodium carbonate can be made by heating sodium bicarbonate: 2NaHCO₃(s) →
Na₂CO₃(s) + CO₂(g) + H₂O(g) at 25°C, ΔH_rxn = 128.9 kJ/mol, ΔG_rxn = 33.1 kJ/mol. Above
what minimum temp will the reaction become spontaneous under standard state conditions?
A. 0.4 K
B. 3.9 K
C. 321 K
D. 401 K
E. 525 K
Correct Answer: D. 401 K
Explanation: For spontaneity, ΔG = 0. Using ΔG = ΔH - TΔS, first calculate ΔS: ΔG = 33.1
kJ/mol, ΔH = 128.9 kJ/mol, T = 298 K. ΔS = (ΔH - ΔG)/T = (128.9 - 33.1)/298 ≈ 0.321
kJ/mol·K. For ΔG = 0, T = ΔH/ΔS = 128.9/0.321 ≈ 401 K.
Questions and Correct Answers
Question 1: Which of the following is an example of a non-spontaneous process?
A. Ice melting at room temperature
B. Sodium metal reacting violently with water
C. Rusting of iron at room temp
D. A ball rolling downhill
E. Water freezing at room temp
Correct Answer: E. Water freezing at room temp
Explanation: A non-spontaneous process requires external energy. At room temperature
(~25°C), water freezing (liquid to solid) is non-spontaneous as the freezing point of water is 0°C
at 1 atm, requiring cooling. Options A, B, C, and D are spontaneous under typical conditions.
Question 2: For the reaction: 2A + B₂ → 2AB, ΔH = +50.0 kJ
A. The reaction is endothermic
B. Heat is released to the surroundings
C. The standard enthalpy of formation for AB is 50.0 kJ
D. The bond energy for each A-B bond is 50.0 kJ
E. The molecule AB contains less energy than A or B₂
Correct Answer: A. The reaction is endothermic
Explanation: A positive ΔH (+50.0 kJ) indicates an endothermic reaction, absorbing heat
from the surroundings. Option B is incorrect (heat is absorbed). Options C, D, and E require
additional data (e.g., formation enthalpies or bond energies) not provided.
Question 3: An endothermic reaction causes the surroundings to:
A. Warm up
B. Become acidic
,C. Condense
D. Decrease in temp
E. Release CO₂
Correct Answer: D. Decrease in temp
Explanation: An endothermic reaction absorbs heat from the surroundings, causing the
surroundings to lose thermal energy and decrease in temperature. Other options are unrelated to
the thermal effects of an endothermic process.
Question 4: Which, if any, of the following processes is spontaneous under the specified
conditions?
A. H₂O(l) → H₂O(s) at 25°C, 1 atm
B. CO₂(s) → CO₂(g) at 0°C, 1 atm
C. 2H₂O(g) → 2H₂(g) + O₂(g) at 25°C, 1 atm
D. C(graphite) → C(diamond) at 25°C, 1 atm
E. None of these are spontaneous
Correct Answer: B. CO₂(s) → CO₂(g) at 0°C, 1 atm
Explanation: Sublimation of CO₂ (dry ice) is spontaneous at 0°C and 1 atm because its
sublimation point is around -78.5°C at 1 atm, and 0°C is well above this. Option A is non-
spontaneous (water freezes below 0°C). Options C and D have high activation energies or
unfavorable thermodynamics at standard conditions.
Question 5: Which is a statement of the second law of thermodynamics?
A. The energy of the universe is constant
B. The entropy of the universe is constant
C. The enthalpy of the universe is constant
D. The energy of the universe is decreasing
E. The entropy of the universe is increasing
Correct Answer: E. The entropy of the universe is increasing
,Explanation: The second law of thermodynamics states that the entropy of the universe
increases for spontaneous processes (ΔS_univ > 0). Option A relates to the first law (energy
conservation).
Question 6: What is ΔS for the reaction SO₃(g) + H₂O(l) → H₂SO₄(aq)?
A. 169.2 J/K
B. 343.2 J/K
C. -169.2 J/K
D. -29.4 J/K
E. 29.4 J/K
Correct Answer: C. -169.2 J/K
Explanation: Entropy decreases (negative ΔS) as the reaction combines a gas and liquid to
form a liquid, reducing molecular freedom. Using standard molar entropies (approximate values:
SO₃(g) ≈ 256 J/mol·K, H₂O(l) ≈ 70 J/mol·K, H₂SO₄(aq) ≈ 157 J/mol·K), ΔS = S_products -
S_reactants = 157 - (256 + 70) ≈ -169 J/K.
Question 7: For a particular process, 28 kJ of heat is absorbed and 15 kJ of work is done on the
surroundings. What is ΔU?
A. ΔU = +43 kJ
B. ΔU = -43 kJ
C. ΔU = -13 kJ
D. ΔU = +13 kJ
E. ΔU = +28 kJ
Correct Answer: D. ΔU = +13 kJ
Explanation: The first law of thermodynamics states ΔU = q + w. Heat absorbed (q = +28 kJ),
work done on surroundings (w = -15 kJ). Thus, ΔU = 28 - 15 = +13 kJ.
Question 8: Which is not a state function?
A. Internal energy
B. Volume
, C. Work
D. Pressure
E. Enthalpy
Correct Answer: C. Work
Explanation: State functions (e.g., internal energy, volume, pressure, enthalpy) depend only
on the current state, not the path. Work depends on the process path, making it a path function.
Question 9: A negative sign for ΔG indicates that, at constant T and P:
A. The reaction is exothermic
B. The reaction is endothermic
C. The reaction is fast
D. The reaction is spontaneous
E. ΔS of the system must be greater than 0
Correct Answer: D. The reaction is spontaneous
Explanation: A negative ΔG (ΔG < 0) indicates a spontaneous reaction at constant
temperature and pressure, per the Gibbs free energy equation (ΔG = ΔH - TΔS).
Question 10: Sodium carbonate can be made by heating sodium bicarbonate: 2NaHCO₃(s) →
Na₂CO₃(s) + CO₂(g) + H₂O(g) at 25°C, ΔH_rxn = 128.9 kJ/mol, ΔG_rxn = 33.1 kJ/mol. Above
what minimum temp will the reaction become spontaneous under standard state conditions?
A. 0.4 K
B. 3.9 K
C. 321 K
D. 401 K
E. 525 K
Correct Answer: D. 401 K
Explanation: For spontaneity, ΔG = 0. Using ΔG = ΔH - TΔS, first calculate ΔS: ΔG = 33.1
kJ/mol, ΔH = 128.9 kJ/mol, T = 298 K. ΔS = (ΔH - ΔG)/T = (128.9 - 33.1)/298 ≈ 0.321
kJ/mol·K. For ΔG = 0, T = ΔH/ΔS = 128.9/0.321 ≈ 401 K.
