Question

For a first order react ion A → product with initial concentration x mol L^-1 , has a half life period of 2.5 hours. For the same reaction with initial concentration mol L^-1 the half life is

(a) (2.5 x 2) hours

(b) \(\Big(\frac{2.5}{2}\Big)\)

(c) 2.5 hours 

(d) Without knowing the rate constant, t_1/2 cannot be determined from the given data

Answer 1

(d) Without knowing the rate constant, t cannot be determined from the given data.

For a first order reaction 

t_1/2 =  \(\frac{0.693}{k}\) t_1/2 does not depend on the initial concentration and it remains constant (whatever may be the initial concentration) 

t_1/2 = 2.5 hrs