Question

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

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

Answer 1

Answer: (C)

$1.25\times {10}^4$ min

The time required to reduce the concentration of 1 M solution to 0.5 M (i.e one-half) is the half life period.

For second order reaction

$t_{1/2}=\frac{1}{k\left[A_0\right]}=\frac{1}{8\times {10}^{-5}{M}^{-1}mi{n}^{-1}\times 1M}=1.25\times {10}^4$ min.