Question

For the reaction,
$A+B\to C$
The concentration of $A$ initially was observed to be $0.2mol/L$ and the concentration of $A$ after $20min$ was found out to be $0.16mol/L$.

Calculate the average rate of reaction $\left(r_{av}\right)$ for first $20min$ in $mol{L}^{-1}mi{n}^{-1}$

• A. $1\times {10}^{-3}$
  
• B. $5\times {10}^{-4}$
• C. $1\times {10}^{-4}$
• D. $2\times {10}^{-3}$

Answer 1

The correct option is D $2\times {10}^{-3}$

Average rate of reaction:
$r_{av}=-\frac{[A{]}_{final}-[A{]}_{initial}}{t_{final}-t_{initial}}=-\frac{\Delta A}{\Delta t}$
Here $[A{]}_{final},[A{]}_{initial}\text{are the concentration of reactant A at}{t}_{final},t_{initial}\text{respectively}$
$r_{av}=-\frac{0.16-0.2}{20}mol{L}^{-1}mi{n}^{-1}$
$r_{av}=2\times {10}^{-3}mol{L}^{-1}mi{n}^{-1}$