Question

The half-life of the radioactive element is 12.5 hour and its quantity is 256 gm. After how much time its quantity will remain 1 gm?

• A. 50 hrs
• B. 100 hrs
• C. 150 hrs
• D. 200 hrs

Answer 1

The correct option is B 100 hrs

No. of half lives required $\Rightarrow \frac{Originlmass}{2^{\left(x\right)}}$

$\Rightarrow \frac{265gm}{2^x}=1gm$

$\Rightarrow x=8$

Half-life = 12.5 hours.

$\therefore$ Total time of reduce $256$ gm to 1gm,

= $12.5\times 8=$ 100 hours.

Hence, option B is correct.