Question

If 75$\%$ of a first-order reaction gets completed in 32 minutes, the time taken for 50$\%$ completion of this reaction is:

• A. 16 minutes
• B. 78 minutes
• C. 8 minutes
• D. 4 minutes

Answer 1

Answer: (C)

8 minutes

Answer 2

$\text{For a first-order reaction, the relationship between time and completion is given by:} \\\ t = \frac{0.693}{k} \\\ \text{For 75\% completion, the time is related to } k \text{ as follows:} \\\ t_{75\%} = \frac{t_{50\%}}{0.693 \times 11} \\\ \text{Given that the 75\% completion time is 32 minutes, the time for 50\% completion is:} \\\ t_{50\%} = \frac{32}{0.693} \approx 8 \, \text{minutes}$