Question

The reaction X $\to$ products follows first order kinetics. In 40 minutes, the concentration of X changes from 0.1 M to 0.025 M. The rate of reaction when concentration of X is 0.01 M is:

• A. $1.73\times {10}^{-4}Mmi{n}^{-1}$
• B. $3.47\times {10}^{-5}Mmi{n}^{-1}$
• C. $3.47\times {10}^{-4}Mmi{n}^{-1}$
• D. $1.73\times {10}^{-5}Mmi{n}^{-1}$

Answer 1

The correct option is C $3.47\times {10}^{-4}Mmi{n}^{-1}$

Explanation :

$k=\frac{2.303}{t}log\frac{a}{a-x}$

$=\frac{2.303}{\left(\text{40 min}\right)}log\frac{\left(0.1M\right)}{\left(0.025M\right)}$

$=\frac{2.303\times 0.6021}{\left(\text{40~min}\right)}=0.03467mi{n}^{-1}$

Rate = k[x]

$=(0.03467,mi{n}^{-1})\times \left(0.01M\right)$

$=3.47\times {10}^{-4}Mmi{n}^{-1}$