CHEM 121 MODULE 9:
THERMOCHEMISTRY,
THERMODYNAMICS, AND KINETICS
QUESTIONS AND ANSWERS 2026/2027
UPDATE || 100% GUARANTEED PASS
1. Which of the following conditions must be met for a chemical reaction to be considered
spontaneous at all temperatures?
A. Positive enthalpy change and positive entropy change
B. Negative enthalpy change and positive entropy change
C. Negative enthalpy change and negative entropy change
D. Positive enthalpy change and negative entropy change
Answer: B
Conceptual Explanation: According to the Gibbs free energy equation (delta G = delta H -
T*delta S), a spontaneous process requires a negative delta G. If enthalpy is negative
(exothermic) and entropy is positive (increasing disorder), delta G will always be negative
regardless of the temperature.
2. What are the units for the rate constant (k) in a third-order reaction?
A. M s^-1
,B. M^-1 s^-1
C. s^-1
D. M^-2 s^-1
Answer: D
Conceptual Explanation: The units of the rate constant are M^(1-n) t^-1. For a third-
order reaction (n=3), the units are M^(1-3) s^-1, which simplifies to M^-2 s^-1.
3. In a bomb calorimeter, the volume is constant. Therefore, the heat measured (qv) is equal
to which thermodynamic property?
A. The change in Enthalpy (delta H)
B. The change in Gibbs Free Energy (delta G)
C. The change in Internal Energy (delta E)
D. The Work (w) done by the system
Answer: C
Conceptual Explanation: At constant volume, no pressure-volume work is done (w=0).
According to the first law of thermodynamics, delta E = q + w, so delta E = qv.
4. According to Boltzmann’s equation, S = k ln W, what does ‘W’ represent?
A. The number of microstates consistent with the macrostate
B. The total energy of the system
, C. The work done by the system
D. The wavelength of the particles
Answer: A
Conceptual Explanation: In statistical mechanics, entropy is a measure of the number of
microstates (W) that correspond to a specific macrostate of a system.
5. What is the sign of delta S for the following reaction: 2 SO2(g) + O2(g) -> 2 SO3(g)?
A. Positive, because disorder increases
B. Negative, because the number of moles of gas decreases
C. Zero, because the reaction is at equilibrium
D. Impossible to determine without enthalpy values
Answer: B
Conceptual Explanation: The reaction proceeds from 3 moles of gas to 2 moles of gas. A
decrease in the number of gas molecules results in a decrease in entropy (delta S < 0).
6. If the activation energy (Ea) of a forward reaction is 50 kJ/mol and the enthalpy change
(delta H) is -20 kJ/mol, what is the activation energy of the reverse reaction?
A. 30 kJ/mol
B. -70 kJ/mol
C. 70 kJ/mol
THERMOCHEMISTRY,
THERMODYNAMICS, AND KINETICS
QUESTIONS AND ANSWERS 2026/2027
UPDATE || 100% GUARANTEED PASS
1. Which of the following conditions must be met for a chemical reaction to be considered
spontaneous at all temperatures?
A. Positive enthalpy change and positive entropy change
B. Negative enthalpy change and positive entropy change
C. Negative enthalpy change and negative entropy change
D. Positive enthalpy change and negative entropy change
Answer: B
Conceptual Explanation: According to the Gibbs free energy equation (delta G = delta H -
T*delta S), a spontaneous process requires a negative delta G. If enthalpy is negative
(exothermic) and entropy is positive (increasing disorder), delta G will always be negative
regardless of the temperature.
2. What are the units for the rate constant (k) in a third-order reaction?
A. M s^-1
,B. M^-1 s^-1
C. s^-1
D. M^-2 s^-1
Answer: D
Conceptual Explanation: The units of the rate constant are M^(1-n) t^-1. For a third-
order reaction (n=3), the units are M^(1-3) s^-1, which simplifies to M^-2 s^-1.
3. In a bomb calorimeter, the volume is constant. Therefore, the heat measured (qv) is equal
to which thermodynamic property?
A. The change in Enthalpy (delta H)
B. The change in Gibbs Free Energy (delta G)
C. The change in Internal Energy (delta E)
D. The Work (w) done by the system
Answer: C
Conceptual Explanation: At constant volume, no pressure-volume work is done (w=0).
According to the first law of thermodynamics, delta E = q + w, so delta E = qv.
4. According to Boltzmann’s equation, S = k ln W, what does ‘W’ represent?
A. The number of microstates consistent with the macrostate
B. The total energy of the system
, C. The work done by the system
D. The wavelength of the particles
Answer: A
Conceptual Explanation: In statistical mechanics, entropy is a measure of the number of
microstates (W) that correspond to a specific macrostate of a system.
5. What is the sign of delta S for the following reaction: 2 SO2(g) + O2(g) -> 2 SO3(g)?
A. Positive, because disorder increases
B. Negative, because the number of moles of gas decreases
C. Zero, because the reaction is at equilibrium
D. Impossible to determine without enthalpy values
Answer: B
Conceptual Explanation: The reaction proceeds from 3 moles of gas to 2 moles of gas. A
decrease in the number of gas molecules results in a decrease in entropy (delta S < 0).
6. If the activation energy (Ea) of a forward reaction is 50 kJ/mol and the enthalpy change
(delta H) is -20 kJ/mol, what is the activation energy of the reverse reaction?
A. 30 kJ/mol
B. -70 kJ/mol
C. 70 kJ/mol
