Question

For certain first-order reaction, 75% of the reaction complete in 30 min. How much time did it require to complete 99.9% of the reaction?

• A. 150 min
• B. 100 min
• C. 90 min
• D. 300 min

Answer 1

The correct option is A 150 min

Its a 1st order reaction, So

$\frac{t_{x\text{\%}}}{t_{y\text{\%}}}=\frac{log\frac{100}{100-x}}{log\frac{100}{100-y}}$

Here x% = 75% and y% = 99.9%

Substituting the values, We get

$\frac{30}{t_{y\text{\%}}}=\frac{log\frac{100}{100-75}}{log\frac{100}{100-99.9}}$

$t_{y\text{\%}}=\frac{30}{0.2}$ = 150 min