The half life of a first order reaction is 2000 years. If the concentration after 8000 years is 0.02 M, then the initial concentration was :

Question

The half life of a first order reaction is 2000 years. If the concentration after 8000 years is 0.02 M, then the initial concentration was : (A) 0.16 M (B) 0.32 M (C) 0.08 M (D) 0.04 M

Tardigrade Admin · Accepted Answer

k =(2.303/ t ) log ([ A ]0/[ A ] t ) (0.693/2000)=(2.303/8000) log ([ A ]0/0.02) ∴[ A ]0=0.32 M

Q. The half life of a first order reaction is $2000$ years. If the concentration after $8000$ years is $0.02 M$ , then the initial concentration was :

$0.16 M$

$0.32 M$

$0.08 M$

$0.04 M$

$k = \frac{2.303}{t} lo g \frac{[ A ] _{0}}{[ A ] _{t}}$
$\frac{0.693}{2000} = \frac{2.303}{8000} lo g \frac{[ A ] _{0}}{0.02}$
$∴ [A]_{0} = 0.32 M$

Q. The half life of a first order reaction is 2000 years. If the concentration after 8000 years is 0.02M, then the initial concentration was :

0.16M

0.32M

0.08M

0.04M