The time for the half-life period of a certain reaction $$A\to$$ products is $$1$$ hour. When the initial concentration of the reactant, $$A$$ is $$2.0\ mol\ L^{-1}$$. How much time does it take initial concentration to make from $$0.50$$ to $$0.25\ mol\ L^{-1}$$ if it is a zero-order reaction?
Correct option is C. $$0.25\ h$$
The initial concentration of A is $$\mathrm{2 \ M}$$.
If the reaction would be first order reaction, then
$$\mathrm{k = \cfrac{a_o - 0.5a_o}{t} = 1}$$
Time taken for the reactant concentration to decrease from 0.5 to 0.25;
$$\mathrm{t = \cfrac{0.5 - 0.25}{k} = \cfrac{0.25}{1}}$$
So, the time taken for reactant concentration to decrease from 0.5 M to 0.25 M is $$0.25 \ h$$.
Hence, Option "C" is the correct answer.