If half-life of a substance is `3.8` days and its quantity is `10.38 gm`. Then substance quantity remaining left after `19` days will be

Options

A. `2.151 g`
B. `0.31` g
C. `1.51` g
D. `0.16` g

Answer

B

Explanation

(b) Number of half -lives `n=(19)/(3.8)=5`
Now , `(N)/(N_(0))=((1)/(2))^(n)`
`implies (N)/(10.38)=((1)/(2))^(5)implies N=10.38xx((1)/(2))^(5)=0.32g`