Question

$\text{A(g)}\xrightarrow{{}}\text{B(g)}$ is a first order reaction. The initial concentration of A is $\text{0}\text{.2}\,\text{mol}\,{{\text{L}}^{-1}}.$ After 10 min, the concentration of B is found to be $\text{0}\text{.18}\,\text{mol}\,{{\text{L}}^{-1}}.$ The rate constant $(in\,mi{{n}^{-1}})$ for the reaction is

• A. 0.2303
• B. 2.303
• C. 0.693
• D. 0.01

Answer 1

Answer: (A)

0.2303

Answer 2

Given, $A(g)\xrightarrow{{}}B(g)$ (first order reaction) Initial concentration of $A=0.2\text{ }mol\text{ }{{L}^{-1}}$ Concentration of $\text{B}=0.18\text{ mol}\,{{\text{L}}^{-1}}$ Concentration of A after 10 min $=0.2-0.18$ $=0.02\text{ mol }{{\text{L}}^{-1}}$ time (r)= 10 min Rate constant, $k=\frac{2.303}{t}\log \frac{a}{a-x}$ $=\frac{2.303}{10}\log \frac{0.2}{0.02}$ $=0.2303\,{{\min }^{-1}}$