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Question: Given below are two statements Statement-I: Order and molecularity for an elementary reaction is eq...

Given below are two statements

Statement-I: Order and molecularity for an elementary reaction is equal Statement-II: Order and molecularity both are defined for a complex reaction. In the light of the above statements, choose the most appropriate answer from the options given below

A

Statement-I is true but Statement-II is false

B

Statement-I is false but Statement-II is true

Answer

Statement-I is true but Statement-II is false

Explanation

Solution

Explanation of the solution:

  1. Analyze Statement-I: "Order and molecularity for an elementary reaction is equal."

    • Elementary Reaction: A reaction that occurs in a single step.
    • Molecularity: The number of reacting species that collide simultaneously in an elementary reaction. It is always a whole number and is derived from the stoichiometry of the elementary step.
    • Order of Reaction: The sum of the powers of the concentration terms of the reactants in the experimentally determined rate law. For an elementary reaction, the rate law can be directly written from its stoichiometry, and thus, the order with respect to each reactant is its stoichiometric coefficient, making the overall order equal to the molecularity.
    • Therefore, Statement-I is True.

  2. Analyze Statement-II: "Order and molecularity both are defined for a complex reaction."

    • Complex Reaction: A reaction that occurs in multiple steps (a sequence of elementary reactions).
    • Molecularity: Molecularity is defined only for each individual elementary step of a reaction, not for the overall complex reaction. A complex reaction does not have a single molecularity.
    • Order of Reaction: The order of reaction is defined for both elementary and complex reactions. For complex reactions, the overall order is determined experimentally and is often governed by the slowest step (rate-determining step) of the reaction mechanism.
    • Since molecularity is not defined for a complex reaction, Statement-II is False.

  3. Choose the most appropriate answer:

    • Statement-I is True.
    • Statement-II is False.
    • This matches option A.

The final answer is A\boxed{A}