Question

If time required to decrease concentration of reactant from 0.8 M to 0.2 M is 12 hours, the half life of this first order reaction is ____________.

Options

• 8 hr

• 12 hr

• 4 hr

• 6 hr

Answer 1

If time required to decrease concentration of reactant from 0.8 M to 0.2 M is 12 hours, the half life of this first order reaction is 6 hr.

Explanation:

Concentration is reduced to 25%. It means it takes two half lives to decrease concentration of reactant from 0.8 M to 0.2 M.

Hence, half life is `12/2` = 6 hours