Reaction Kinetics

Reaction Kinetics MDCAT MCQs with answers

63 past paper MCQs from Chemistry unit 7, Reaction Kinetics, across 4 topics. They are arranged topic by topic; bigger topics show a sample here and link to their full set and to study notes. Tap “Show answer” for the correct option and a short solution.

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Chemical Kinetics

1.The rate of a reaction: (MDCAT 2020)

  1. increases as the reaction proceeds
  2. decreases as the reaction proceeds
  3. remains the same
  4. may decrease or increase
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Correct answer: (b) decreases as the reaction proceeds

The reactants are being used up, so their concentrations and with them the rate fall as the reaction goes on.

2.The rate of reaction between two specific time intervals is called the: (MDCAT 2023)

  1. instantaneous rate of reaction
  2. rate of reaction
  3. average rate of reaction
  4. specific rate of reaction
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Correct answer: (c) average rate of reaction

A change measured over an interval rather than at an instant is the average rate.

3.Identify the correct formula to calculate the rate of a reaction: (MDCAT 2024)

  1. change in concentration of substance $\div$ time taken for the change
  2. time taken for the change $\div$ change in concentration of substance
  3. time taken for the change $\div$ change in concentration $\times100$
  4. time taken for the change $\times$ change in concentration
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Correct answer: (a) change in concentration of substance $\div$ time taken for the change

Rate is the change in concentration per unit time.

All 21 Chemical Kinetics MCQs → Chemical Kinetics notes →

Factors Affecting the Rate of Reaction

4.In a reversible reaction, a catalyst lowers the activation energy of the: (MDCAT 2020)

  1. forward reaction
  2. reverse reaction
  3. forward as well as the reverse reaction
  4. forward reaction but raises that of the reverse reaction
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Correct answer: (c) forward as well as the reverse reaction

The catalyst offers a lower path between the same two states, so both directions are speeded up equally and the equilibrium is unmoved.

5.A catalyst which is in the same phase as the reactants is known as: (MDCAT 2022)

  1. a heterogeneous catalyst
  2. a homogeneous catalyst
  3. a slow catalyst
  4. a fast catalyst
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Correct answer: (b) a homogeneous catalyst

One phase throughout is what homogeneous means.

6.The rate of a chemical reaction changes with: (KMU MDCAT 2025)

  1. Concentration of reactant molecules
  2. Concentration of product molecules
  3. Concentration of both reactant and product
  4. Rate constant
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Correct answer: (a) Concentration of reactant molecules

The rate law is written in the concentrations of the reactants alone.

All 12 Factors Affecting the Rate of Reaction MCQs → Factors Affecting the Rate of Reaction notes →

Order of Reaction

7.Consider the hypothetical equation $aA+bB\to cC+dD$. Which of the following represents the correct rate equation? (MDCAT 2024)

  1. Rate $=k[A][B]$
  2. Rate $=k[A]^a[B]^b$
  3. Rate $=k[A]^a$
  4. Rate $=k[B]^b$
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Correct answer: (b) Rate $=k[A]^a[B]^b$

For an elementary step the order in each reactant is its coefficient, so the rate law carries both concentrations raised to those powers.

8.If a reaction rate does not change with concentration, then it is: (MDCAT 2024)

  1. third order
  2. second order
  3. first order
  4. zero order
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Correct answer: (d) zero order

A rate independent of concentration is $\text{rate}=k[A]^0$, which is zero order.

9.A reaction is first order with respect to A and third order with respect to B, the rate equation is: (NUMS MDCAT 2025)

  1. Rate = K[A][B]2
  2. Rate = K[A]2[B]
  3. Rate = K[A][B]3
  4. Rate = K[A]
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Correct answer: (c) Rate = K[A][B]3

The rate law carries each concentration to the power of its own order.

All 18 Order of Reaction MCQs → Order of Reaction notes →

Rate Constant

10.The effect of temperature on the rate of a reaction is given by: (MDCAT 2020)

  1. Henderson's equation
  2. the general gas equation
  3. the Arrhenius equation
  4. the van der Waals equation
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Correct answer: (c) the Arrhenius equation

$k=Ae^{-E_a/RT}$ is the Arrhenius equation.

11.Which of the following is the CORRECT Arrhenius equation? (MDCAT 2024)

  1. $k=Ae^{-E_a/QT}$
  2. $k=Ae^{-E_a/RT}$
  3. $k=Ae^{-E_a/ST}$
  4. $k=Ae^{-E_a/uT}$
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Correct answer: (b) $k=Ae^{-E_a/RT}$

$k=Ae^{-E_a/RT}$, with $R$ the gas constant and $E_a$ the activation energy.

12.The specific rate constant (k) of a reaction is related to the concentration of reactants: (KMU MDCAT 2025)

  1. Directly
  2. Inversely
  3. Exponentially
  4. Independently
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Correct answer: (d) Independently

The rate constant depends on temperature and on the catalyst, never on how much reactant is present.

All 12 Rate Constant MCQs → Rate Constant notes →

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