Question

For the zero order reaction $A\to B+C$ : initial concentration of $A$ is $0.1M$. If $A=0.08M$ after $10\text{minutes}$, then its half-life and completion time are respectively :

• A. $10\text{min};20\text{min}$
• B. $2\times {10}^{-3}\text{min};4\times {10}^{-3}\text{min}$
  
• C. $25\text{min};50\text{min}$
• D. $250\text{min};500\text{min}$

Answer 1

The correct option is C $25\text{min};50\text{min}$

Given intial concentration is $0.1M$
After , $10\text{min}$ concentration is $0.08M$
$\therefore \text{Change in concentration,}dx=0.1-0.08=0.02M$
So rate constant of the reaction is
$k=\frac{x}{t}=\frac{0.02}{10}=2\times {10}^{-3}{\text{M min}}^{-1}$
$\therefore t_{\frac{1}{2}}=\frac{{\left[A\right]}_0}{2k}=\frac{0.1}{2\times 2\times {10}^{-3}}=25\text{min}$
$\therefore t_{\text{completion}}=2\times t_{\frac{1}{2}}=50\text{min}$