Question

For the reaction $A\to$ products, $-\frac{d\left[A\right]}{dt}=k$ and at different time intervals, $\left[A\right]$ values are

Time	0	5 min	10 min	15 min
[A]	20 mol	18 mol	16 mol	14 mol

At 20 min, the rate would be:

• A. 12 mol/min
• B. 10 mol/min
• C. 8 mol/min
• D. 0.4 mol/min

Answer 1

The correct option is D 0.4 mol/min

For every 5 minute interval, the concentration changes by 2 moles per litre.
Hence, the rate of reaction is constant throughout.
$\text{Rate}=\frac{\text{Change in concentration}}{\text{Time interval}}=\frac{2}{5}=0.4$ mol/min.