Questions about Reaction Order
Multiple-Choice Questions: Reaction Order
1. What does the order of a reaction indicate?
A) The number of products
B) The number of steps in the mechanism
C) The dependence of the reaction rate on reactant concentrations
D) The energy required to break bonds
E) The direction of the reaction
2. In the rate law: Rate = k[A]^2[B], what is the overall order of the reaction?
A) 1
B) 2
C) 3
D) 0
E) Cannot be determined
3. A reaction is first-order in A. If [A] is doubled, the rate will:
A) Stay the same
B) Double
C) Triple
D) Quadruple
E) Be halved
4. A reaction is zero-order in [B]. What happens to the rate when [B] is increased?
A) It doubles
B) It increases fourfold
C) It is halved
D) It remains the same
E) It triples
5. The sum of the exponents in a rate law expression gives the:
A) Half-life
B) Number of steps
C) Reaction order
D) Activation energy
E) Equilibrium constant
6. If a reaction has Rate = k[A]^0[B]^2, what is the order with respect to A?
A) First
B) Second
C) Zero
D) Third
E) Cannot be determined
7. What is the overall order of the reaction with rate law: Rate = k[A][B]^0?
A) 0
B) 1
C) 2
D) Cannot be determined
E) 3
8. Which experimental method is commonly used to determine reaction order?
A) Titration
B) Rate-concentration data
C) Flame test
D) Melting point analysis
E) Density measurement
9. In Rate = k[A]^1[B]^2, the reaction is:
A) First-order overall
B) Second-order overall
C) Third-order overall
D) Zero-order overall
E) Fourth-order overall
10. If doubling [A] increases the rate by a factor of 4, what is the reaction order with respect to A?
A) Zero
B) First
C) Second
D) Third
E) Cannot be determined
11. Which of the following is true for a zero-order reaction?
A) The rate depends on concentration
B) The rate is constant
C) The rate increases with time
D) The rate depends on temperature only
E) The rate is inversely proportional to concentration
12. If the units of the rate constant k are s⁻¹, what is the order of the reaction?
A) Zero
B) First
C) Second
D) Third
E) Cannot be determined
13. Which graph is linear for a first-order reaction?
A) Rate vs. [A]
B) ln[A] vs. time
C) 1/[A] vs. time
D) [A] vs. time
E) Rate vs. time
14. What are the units of the rate constant k for a second-order reaction?
A) mol/L
B) s⁻¹
C) L·mol⁻¹·s⁻¹
D) mol·L⁻¹·s⁻¹
E) L·mol⁻²·s
15. Which of the following is a correct rate law for a third-order reaction overall?
A) Rate = k[A]^3
B) Rate = k[A][B]^2
C) Rate = k[A]^2[B]
D) All of the above
E) None of the above
16. What information does reaction order provide?
A) Mechanism of the reaction
B) Thermodynamic favorability
C) How concentration affects rate
D) Catalyst used
E) Volume change
17. If the rate remains unchanged when [A] is changed, what is the order with respect to A?
A) First
B) Second
C) Zero
D) Third
E) Undefined
18. For a second-order reaction, how is the rate affected when the concentration of the reactant is tripled?
A) No change
B) It doubles
C) It increases ninefold
D) It triples
E) It decreases
19. Which of the following statements about reaction order is FALSE?
A) Reaction order is determined experimentally
B) Reaction order can be a fraction
C) Reaction order must be positive
D) Reaction order is not necessarily the same as stoichiometric coefficients
E) Reaction order affects the units of k
20. If the rate law is Rate = k[A]^1/2, what is the order of the reaction with respect to A?
A) 0
B) 1
C) 2
D) 1/2
E) Cannot be determined
- Questions on Activation Energy and Activated Complex
- Questions about Catalysts
- Questions about Rate Law and Rate Constant
Answer Key with Explanations
1. C – Reaction order tells us how the rate depends on the concentration of reactants.
2. C – 2 (for A) + 1 (for B) = 3 (third-order overall).
3. B – First-order: rate is directly proportional to [A].
4. D – Zero-order: rate is independent of [B].
5. C – The sum of the exponents gives the overall reaction order.
6. C – Any species with exponent 0 has zero-order.
7. B – Exponent of A is 1; B is 0 → 1st-order overall.
8. B – Rate-concentration studies are used to find reaction order.
9. C – 1 (A) + 2 (B) = 3 (third-order).
10. C – 2² = 4 → second-order dependence.
11. B – In zero-order reactions, rate is constant regardless of concentration.
12. B – s⁻¹ is the unit of first-order rate constant.
13. B – For first-order, ln[A] vs. time is linear.
14. C – Second-order: L·mol⁻¹·s⁻¹.
15. D – All expressions shown represent third-order reactions.
16. C – Reaction order describes the effect of concentration on rate.
17. C – If rate doesn't change with [A], it is zero-order in A.
18. C – 3² = 9 → rate increases ninefold.
19. C – Reaction orders can be negative or fractional. So this is false.
20. D – Exponent of 1/2 means half-order in A.
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