Question

The half-life period of a first order reaction is $15$ minutes. The amount of substance left after one hour will be :

• A. 1/4 of the original amount
• B. 1/8 of the original amount
• C. 1/16 of the original amount
• D. 1/32 of the original amount

Answer 1

Answer: (C)

Since : $t_{1/2} =15 \,min$

$\therefore $ No.of half lives $=\frac{60}{15}=4$

$\therefore $ Amount of substance left after one hour

$=\frac{A_{0}}{\left(2\right)^{n}}=\frac{A_{0}}{\left(2\right)^{4}}=\frac{A_{0}}{16}$