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NEET Chemistry · Chemical Kinetics

Order, molecularity and the rate law

Taught in NCERT Class 12 Chemistry, Chapter 3: Chemical Kinetics.

1 verified question: Easy 0 · Medium 1 · NEET level 0

Sample questions

Sample 1Medium

Which one of the following statements about order and molecularity is correct?

  1. A

    The order of a reaction can be zero or fractional, but molecularity cannot be zero or fractional.

  2. B

    Molecularity of a reaction can be determined only experimentally.

  3. C

    For a complex reaction, the molecularity of the overall reaction equals its order.

  4. D

    The order of a reaction is always equal to the sum of the stoichiometric coefficients in the balanced equation.

Show the answer
The answer is A.

Order is an experimental quantity and can be 0, a fraction or an integer. Molecularity is the number of species colliding in an elementary step, so it must be a whole number of at least one.

  • B.

    It is the order that is found experimentally; molecularity is a theoretical count for an elementary step.

  • C.

    Molecularity has no meaning for an overall complex reaction; it applies only to elementary steps.

  • D.

    Order is determined from the experimental rate law and need not match the stoichiometric coefficients.

NCERT: Class 12 Chemistry, Chapter 3, 3.2

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