Question

If 75% of a first order reaction completed in 15 min. Then 90% of the same reaction completed in-

• A. 20 min
• B. 25 min
• C. 30 min
• D. 150 min

Answer 1

Answer: (B)

25 min

Answer 2

t_1/2 = $\frac{15}{2}$min t_90% = $\frac{10}{3} \times t_{1/2}$ = $\frac{10}{3} \times \frac{15}{2}$ = 25 min