When initial concentration of a reactant is doubled in a reaction, its half-life period is not affected. The order of the reaction is:

Step-by-step solution

t 1 / 2 ∝ 1 a 0 n - 1 t 1 / 2 is independent of initial concentration i.e. t 1 / 2 ∝ 1 a 0 1 - 1 (is constant) i.e n = 1 (order of reaction)