Question

The reaction $A\to B$ follows first-order kinetics. The time taken for 0.8 mol of A to produce 0.6 mol of B is 1 hr. What is the time taken for the conversion of 0.9 mol of A to produce 0.675 mol of B?

• A. 1 hr
• B. 0.5 hr
• C. 0.25 hr
• D. 2 hr

Answer 1

Answer: (A)

1 hr

Time for the conversion of 0.8 mol of A to 0.6 mol of B :
$B=\frac{0.6}{0.8}=0.75=t_{75\%}$
Similarly, time for the conversion of 0.9 mol of A to 0.675 mol of B = $\frac{0.675}{0.9}=0.75=t_{75\%}$
Hence, $t_{75\%}$ in both case $=1hr$.