Question

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

• A. $150\, min$
• B. $100\, min$
• C. $90\, min$
• D. $300\, min$

Answer 1

Answer: (A)

$150\, min$

Answer 2

Its a 1st order reaction, So

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

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

Substituting the values, We get

$\frac{30}{t_{y} \%}=\frac{\log \frac{100}{100-75}}{\log \frac{100}{100-99.9}}$
$t _{ y \%}=\frac{30}{0.2}=150 min$