JEE Main · 2020 · Shift-ImediumCK-070

It is true that:

Chemical Kinetics · Class 12 · JEE Main Previous Year Question

Question

It is true that:

Options
  1. a

    A second order reaction is always a multistep reaction

  2. b

    A zero order reaction is a multi-step reaction

  3. c

    A first order reaction is always a single step reaction

  4. d

    A zero order reaction is a single step reaction

Correct Answerb

A zero order reaction is a multi-step reaction

Detailed Solution

Analysis of each statement:

(1) FALSE — A second order reaction can be elementary (single step), e.g., 2HIH2+I2\mathrm{2HI \rightarrow H_2 + I_2}.

(2) TRUE — A zero order reaction cannot be an elementary reaction (elementary reactions must have order equal to molecularity, which is at least 1). Therefore, a zero order reaction must be a multi-step (complex) reaction where the rate-determining step involves a catalyst or surface.

(3) FALSE — A first order reaction can be multi-step (e.g., radioactive decay is first order and elementary, but many first order reactions are complex).

(4) FALSE — Same reasoning as (2); zero order reactions are multi-step.

Answer: Option (2)

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