Question

A reactant decomposes with a half-life of 27.5 s when its initial concentration is 0.239 M. When the initial concentration is 0.667 M, this same reactant decomposes with a half‑life of 76.7 s.

What is the order of the reaction? What is the value and unit of the rate constant for this reaction?

Answer 1

from the given data it is clear

half life is inversy proportional to initial concentration.

so order of the reaction = 2

for second order

K = 1 / [A₀]t_1/2

K = 1 / [0.239] x 27.5

K = 1 / 6.57

K = 0.152 M^-1 s^-1