Question

In a reaction, the concentration of a reactant (A) changes from $0.200mol{L}^{-1}$ to $0.150mol{L}^{-1}$ in 10 minutes. What is the average rate of reaction during this interval ?

• A. $0.005\text{mol}{L}^{-1}{\text{min}}^{-1}$
• B. $0.05\text{mol}{L}^{-1}{\text{min}}^{-1}$
• C. $0.01\text{mol}{L}^{-1}{\text{min}}^{-1}$
• D. $0.5\text{mol}{L}^{-1}{\text{min}}^{-1}$

Answer 1

The correct option is A $0.005\text{mol}{L}^{-1}{\text{min}}^{-1}$

$\Delta A=[A{]}_{final}-[A{]}_{initial}$
$\Delta A=[0.150-0.200]=-0.050\text{mol}{L}^{-1}$
$\Delta t=10$ min

$\text{Average rate of reaction}=\frac{-\Delta A}{\Delta t}=\frac{-[-0.050]}{10}$

$\text{Average rate of reaction}=\frac{0.050}{10}=0.005\text{mol}{L}^{-1}{\text{min}}^{-1}$

Thus option (a) is correct.