Question

The rate constant for a second order reaction is $8\times {10}^{-5}{M}^{-1}{min}^{-1}$. How long will it take a 1M solution to be reduced to 0.5 M in reactant ?

• A. $8.665\times {10}^{3}min$
• B. $8\times {10}^{-5}min$
• C. $1.25\times {10}^{4}min$
• D. $4\times {10}^{-5}min$

Answer 1

The correct option is C $1.25\times {10}^{4}min$

Given that,

$K=8\times {10}^{-5}{M}^{-1}{min}^{-1}$

$a_0=1M,a_t=0.5M$

Now, for the second-order reaction.

$\frac{1}{a_t}=\frac{1}{a_0}+Kt$

Substituting the value we get,

$\frac{1}{0.5}=\frac{1}{1}+8\times {10}^{-5}\times t$

$t=1.25\times {10}^4$