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NEET Chemistry: Arrhenius theory and activation energy Practice Questions

13 free multiple-choice questions on Arrhenius theory and activation energy (Reactions and Kinetics) for NEET Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.

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  1. Q1. Arrhenius theory explains the dependence of reaction rate on temperature. Which physical principle forms the basis for this temperature dependence?

    • AConservation of Momentum.
    • BThe principle of quantization of energy.
    • CThe concept of random thermal motion and energy distribution.
    • DLaw of Conservation of Mass.
    Show answer & explanation

    Correct answer: C — The concept of random thermal motion and energy distribution.

    The temperature dependence of reaction rates is based on the distribution of kinetic energies among the molecules. At higher temperatures, a larger fraction of molecules possess the necessary energy to react, which is governed by random thermal motion.

  2. Q2. Collision theory states that for a reaction to occur, the colliding molecules must have sufficient energy. What is the minimum energy required for a collision to be considered effective?

    • AThe total kinetic energy of the system
    • BThe energy of the reactants
    • CThe activation energy
    • DThe enthalpy change of the reaction
    Show answer & explanation

    Correct answer: C — The activation energy

    For a collision to be effective and lead to a reaction, the colliding molecules must possess at least the activation energy (Eₐ).

  3. Q3. Which of the following statements correctly describes the relationship between temperature and the rate of a reaction according to the Arrhenius concept?

    • AAs temperature increases, the rate of reaction generally increases
    • BAs temperature increases, the rate of reaction decreases
    • CThe rate of reaction is inversely proportional to the activation energy
    • DThe rate of reaction is independent of temperature
    Show answer & explanation

    Correct answer: A — As temperature increases, the rate of reaction generally increases

    Generally, increasing the temperature increases the fraction of molecules possessing energy greater than Eₐ, thus increasing the reaction rate.

  4. Q4. Which factor is primarily responsible for the increase in the rate of a reaction when the temperature is raised?

    • Athe decrease in the system's volume
    • Bthe increase in the fraction of molecules with energy greater than Eₐ
    • Cthe decrease in the frequency of collisions
    • Dthe increase in the density of the reactants
    Show answer & explanation

    Correct answer: B — the increase in the fraction of molecules with energy greater than Eₐ

    Raising the temperature increases the average kinetic energy, thereby increasing the fraction of molecules that possess the necessary energy (Eₐ) to successfully react upon collision.

  5. Q5. Which statement accurately describes the relationship between temperature and the fraction of molecules possessing energy greater than the activation energy (Eₐ) for a reaction?

    • AThe activation energy (Eₐ) is inversely proportional to the temperature.
    • BThe fraction of molecules with energy > Eₐ increases exponentially with increasing temperature.
    • CThe fraction of molecules with energy < Eₐ decreases exponentially with increasing temperature.
    • DThe reaction rate is directly proportional to the absolute temperature.
    Show answer & explanation

    Correct answer: B — The fraction of molecules with energy > Eₐ increases exponentially with increasing temperature.

    According to the Arrhenius theory, the fraction of molecules that can successfully react is proportional to the Boltzmann factor, e⁽-Eₐ/RT). As temperature (T) increases, the term -Eₐ/RT becomes less negative, leading to an exponential increase in the fraction of molecules with sufficient energy to overcome the activation energy, thus increasing the reaction rate.

  6. Q6. When the temperature of a reaction is increased, what happens to the fraction of molecules that possess energy equal to or greater than the activation energy (Eₐ)?

    • AIt decreases
    • BIt becomes zero
    • CIt remains unchanged
    • DIt increases
    Show answer & explanation

    Correct answer: D — It increases

    According to the Arrhenius theory, increasing the temperature increases the kinetic energy of the molecules. This results in a larger fraction of molecules having sufficient energy to overcome the activation energy barrier and participate in the reaction.

  7. Q7. What is the primary physical requirement for a reaction to occur according to the Arrhenius theory?

    • ALow pressure of the system
    • BPresence of a catalyst
    • CHigh concentration of reactants
    • DSufficient kinetic energy of colliding molecules
    Show answer & explanation

    Correct answer: D — Sufficient kinetic energy of colliding molecules

    According to the Arrhenius theory, for a reaction to proceed, the colliding molecules must possess a minimum amount of kinetic energy, which is related to the activation energy (Eₐ).

  8. Q8. Which statement best describes the role of activation energy (Eₐ) in chemical reaction kinetics?

    • AIt is solely dependent on the system's temperature.
    • BIt represents the minimum energy barrier that must be overcome for a reaction to occur.
    • CIt determines the total energy content of reactants.
    • DIt is inversely proportional to the reaction rate.
    Show answer & explanation

    Correct answer: B — It represents the minimum energy barrier that must be overcome for a reaction to occur.

    Activation energy is the minimum energy requirement that the reactants must possess in order to successfully transition over the energy barrier and form products, thus controlling the rate of reaction.

  9. Q9. For a chemical reaction to occur, what is the minimum amount of energy that must be supplied to the colliding molecules?

    • AThe enthalpy change (ΔH) of the reaction
    • BThe total energy of the reactants
    • CThe activation energy (Eₐ)
    • DThe potential energy of the products
    Show answer & explanation

    Correct answer: C — The activation energy (Eₐ)

    The activation energy (Eₐ) is the minimum kinetic energy required for reactant molecules to overcome the energy barrier and successfully react.

  10. Q10. The Arrhenius equation mathematically links the rate constant (k) with the activation energy (Eₐ) and temperature (T). Which form of the equation is most relevant for understanding the dependence of the rate on temperature?

    • AEₐ = RT ln k
    • Bk = A e⁽-Eₐ/RT)
    • CΔG = ΔH - T ΔS
    • DP = nRT
    Show answer & explanation

    Correct answer: B — k = A e⁽-Eₐ/RT)

    The standard Arrhenius equation, k = A e⁽-Eₐ/RT), explicitly shows the exponential dependence of the rate constant (k) on the inverse of the activation energy divided by the temperature (T).

  11. Q11. According to the Arrhenius theory, what is the fundamental role of activation energy (Eₐ) in a chemical reaction?

    • AIt is the total energy released during the reaction.
    • BIt represents the minimum energy required for reactants to be converted into products.
    • CIt determines the enthalpy change (ΔH) of the reaction.
    • DIt is the change in potential energy per unit volume.
    Show answer & explanation

    Correct answer: B — It represents the minimum energy required for reactants to be converted into products.

    Activation energy (Eₐ) is the minimum amount of energy that must be supplied to the reacting molecules for the reaction to occur. It acts as an energy barrier that must be overcome.

  12. Q12. The activation energy (Eₐ) for a chemical reaction represents which of the following?

    • AThe equilibrium constant of the reaction.
    • BThe potential energy stored in the reactants.
    • CThe minimum energy barrier that must be overcome for the reaction to proceed.
    • DThe total energy released during the reaction.
    Show answer & explanation

    Correct answer: C — The minimum energy barrier that must be overcome for the reaction to proceed.

    Activation energy (Eₐ) is the minimum energy required to initiate a chemical reaction; it is the energy barrier that must be overcome for reactants to transform into products.

  13. Q13. For a reaction to occur, what minimum condition must be met regarding the kinetic energy of the colliding molecules, according to the Arrhenius concept?

    • Athe kinetic energy must be equal to the potential energy of the products
    • Bthe total kinetic energy must be zero
    • Cthe kinetic energy must be greater than the activation energy (Eₐ)
    • Dthe molecules must be moving in phase
    Show answer & explanation

    Correct answer: C — the kinetic energy must be greater than the activation energy (Eₐ)

    According to collision theory, successful reaction requires that the colliding molecules possess kinetic energy equal to or greater than the activation energy (Eₐ) to overcome the energy barrier.

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