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 : $t_{1/2}=15min$

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

$\therefore$ Amount of substance left after one hour

$=\frac{A_0}{{\left(2\right)}^n}=\frac{A_0}{{\left(2\right)}^4}=\frac{A_0}{16}$