Asked in Premeth Test 23 — Chemical Kinetics and Chemical Equilibrium (25 March 2025) 2025Moderate

The unit of rate constant for the first-order reaction is:

Correct answer: C. s-1

  • A. conc.s-1
  • B. M2s-1
  • C. s-1
  • D. M-1s-1
  • E. M-1s-2

Explanation

The unit of the rate constant for a first-order reaction is s-1. This is because, for a first-order reaction, the rate is directly proportional to the concentration of one reactant, and the order of the reaction dictates the units of the rate constant. For a first-order reaction, the units of the rate (M s-1) divided by the concentration (M) give the rate constant units of s-1. Other options, like M2s-1 and M-1s-1, correspond to higher-order reactions or are not applicable to standard reaction orders.

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About Rate Constant

The rate constant, k, connects reaction rate with reactant concentrations in a rate law and has a value fixed for a particular reaction at a given temperature. Questions involve determining k from rate data, identifying its units for different reaction orders, and applying the Arrhenius equation to temperature changes.

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