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Chemical Kinetics and Nuclear Chemistry question

2025 · 3 Apr · Shift 2 · Q11
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Chemical Kinetics and Nuclear Chemistry question

2025 · 3 Apr · Shift 2 · Q11

JEE MainChemistryChemical Kinetics and Nuclear ChemistryMCQ+4 / −1
Consider the following statements related to temperature dependence of rate constants. Identify the correct statements. A. The Arrhenius equation holds true only for an elementary homogenous reaction. B. The unit of AAA is same as that of kkk in Arrhenius equation. C. At a given temperature, a low activation energy means a fast reaction. D. A and Ea as used in Arrhenius equation depend on temperature. E. When Ea≫RT,A\mathrm{Ea} \gg \mathrm{RT}, \mathrm{A}Ea≫RT,A and Ea become interdependent. Choose the correct answer from the options given below:
  1. A
    A, C and D Only
  2. B
    B, D and E Only
  3. C
    B and C Only
  4. D
    A and B Only
View written solutionFree

Correct answer: C

  1. Write the Arrhenius equation

    The Arrhenius equation is k=Ae−Ea/(RT)k = A e^{-E_a/(RT)}k=Ae−Ea​/(RT) where:

    • kkk = rate constant
    • AAA = pre-exponential (frequency) factor
    • EaE_aEa​ = activation energy
    • RRR = gas constant
    • TTT = temperature
  2. Check each statement

    Statement A

    "The Arrhenius equation holds true only for an elementary homogeneous reaction."

    This is false.

    The Arrhenius equation is an empirical relation and is widely applicable to many reactions, not only elementary homogeneous reactions.

    Statement B

    "The unit of AAA is same as that of kkk in Arrhenius equation."

    This is true.

    Since in k=Ae−Ea/(RT)k = A e^{-E_a/(RT)}k=Ae−Ea​/(RT) the exponential term is dimensionless, AAA must have the same units as kkk.

    Statement C

    "At a given temperature, a low activation energy means a fast reaction."

    This is true.

    From k=Ae−Ea/(RT)k = A e^{-E_a/(RT)}k=Ae−Ea​/(RT) for fixed TTT, a smaller EaE_aEa​ gives a larger value of kkk, hence the reaction is faster.

    Statement D

    "AAA and EaE_aEa​ as used in Arrhenius equation depend on temperature."

    This is false in the usual JEE treatment.

    In the Arrhenius equation, for a given reaction over a moderate temperature range, AAA and EaE_aEa​ are treated as constants.

    Statement E

    "When Ea≫RTE_a \gg RTEa​≫RT, AAA and EaE_aEa​ become interdependent."

    This is false.

    In the standard Arrhenius formulation, AAA and EaE_aEa​ are taken as independent parameters. The condition Ea≫RTE_a \gg RTEa​≫RT does not imply such interdependence.

  3. List the correct statements

    The correct statements are: B and C\boxed{B \text{ and } C}B and C​

  4. Match with options

    Option C says: B and C Only.

    Hence the correct option is C\boxed{\text{C}}C​

  5. Compare with stored correct answer

    Stored correct answer: C

    Our derived answer matches the stored answer.

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