Nuclear Chemistry Ques 12

12. A human body required $0.01$ $M$ activity of radioactive substance after $24$ hours. Half life of radioactive substance is $6$ hours. Then injection of maximum activity of radioactive substance that can be injected will be

[2001]

(a) $0.08 $ $M$

(b) $0.04 $ $M$

(c) $0.32 $ $M$

(d) $0.16 $ $M$

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Answer:

Correct Answer: 12.(d)

Solution:

  1. (d) Remaining activity $=0.01 $ $M$

after $24$ $ hrs$

Remaining activity $=$ Initial activity $\times(\frac{1}{2})^{n}$

Used half life time $(n)=\frac{\text{ Total time }}{T _{1 / 2}}=\frac{24}{6}=4$

So, $\quad 0.01=$ Initial activity $\times(\frac{1}{2})^{4}$

Initial activity $=0.01 \times 16=0.16 $ $M$