CHEM 104 MODULE 8 PRACTICE EXAM
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2025
1. Which factor does NOT affect the rate of a chemical reaction?
A. Temperature
B. Color of reactants
C. Concentration of reactants
D. Presence of a catalyst
Color does not impact reaction rate; rate is influenced by kinetic and
energetic factors.
2. What happens to the rate of a reaction when the temperature is
increased?
A. It decreases
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, B. It remains constant
C. It increases
D. It stops
Higher temperature increases molecular motion and collision energy,
accelerating the reaction.
3. The rate law for a reaction is rate = k[A][B]². What is the overall order of
the reaction?
A. Zero
B. Third
C. First
D. Second
The exponents add up: 1 (for A) + 2 (for B) = 3rd order.
4. Which of the following is a unit for a first-order rate constant (k)?
A. s⁻¹
B. M⁻¹s⁻¹
C. M/s
D. mol/L
For a first-order reaction, the rate constant has units of s⁻¹.
5. A catalyst affects a chemical reaction by:
A. Changing the equilibrium constant
B. Increasing the temperature
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, C. Lowering the activation energy
D. Providing reactants
A catalyst lowers the activation energy without altering the equilibrium.
6. The half-life of a first-order reaction is:
A. Dependent on initial concentration
B. Constant
C. Inversely proportional to concentration
D. Doubled each cycle
First-order reactions have a constant half-life regardless of concentration.
7. At equilibrium, the concentrations of reactants and products:
A. Remain constant
B. Are equal
C. Decrease
D. Increase
Equilibrium means forward and reverse reaction rates are equal, so
concentrations stay constant.
8. Which expression is correct for the equilibrium constant (K) of the
reaction: N₂ + 3H₂ ⇌ 2NH₃?
A. K = [N₂][H₂]³ / [NH₃]²
B. K = [NH₃] / [N₂][H₂]
C. K = [NH₃]² / [N₂][H₂]³
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QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2025
1. Which factor does NOT affect the rate of a chemical reaction?
A. Temperature
B. Color of reactants
C. Concentration of reactants
D. Presence of a catalyst
Color does not impact reaction rate; rate is influenced by kinetic and
energetic factors.
2. What happens to the rate of a reaction when the temperature is
increased?
A. It decreases
1|Page
, B. It remains constant
C. It increases
D. It stops
Higher temperature increases molecular motion and collision energy,
accelerating the reaction.
3. The rate law for a reaction is rate = k[A][B]². What is the overall order of
the reaction?
A. Zero
B. Third
C. First
D. Second
The exponents add up: 1 (for A) + 2 (for B) = 3rd order.
4. Which of the following is a unit for a first-order rate constant (k)?
A. s⁻¹
B. M⁻¹s⁻¹
C. M/s
D. mol/L
For a first-order reaction, the rate constant has units of s⁻¹.
5. A catalyst affects a chemical reaction by:
A. Changing the equilibrium constant
B. Increasing the temperature
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, C. Lowering the activation energy
D. Providing reactants
A catalyst lowers the activation energy without altering the equilibrium.
6. The half-life of a first-order reaction is:
A. Dependent on initial concentration
B. Constant
C. Inversely proportional to concentration
D. Doubled each cycle
First-order reactions have a constant half-life regardless of concentration.
7. At equilibrium, the concentrations of reactants and products:
A. Remain constant
B. Are equal
C. Decrease
D. Increase
Equilibrium means forward and reverse reaction rates are equal, so
concentrations stay constant.
8. Which expression is correct for the equilibrium constant (K) of the
reaction: N₂ + 3H₂ ⇌ 2NH₃?
A. K = [N₂][H₂]³ / [NH₃]²
B. K = [NH₃] / [N₂][H₂]
C. K = [NH₃]² / [N₂][H₂]³
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