Question

300 gram of a radioactive sample has a half-life of 3 hours. After 18 hours, the remaining quantity will be :

• A. 4.68 gram
• B. 2.34 gram
• C. 3.34 gram
• D. 9.37 gram

Answer 1

Answer: (A)

4.68 gram

Original quantity of radioactive substance = 300 grams.

Half-life = 3 hours.

No. of half lives in 18 hours $\Rightarrow \frac{18}{3}=6$

After 18 hours, $\frac{1}{{\left(2\right)}^6}$ of the original would be remaining $\Rightarrow \frac{1}{64}\times 300gm\Rightarrow 4.6875grams.$