Question

A human body required the 0.01 M activity of radioactive substance after 24 h. Half-life of radioactive substance is 6 h. Then, injection of maximum activity of radioactive substance that can be injected will be

• A. 0.08
• B. 0.04
• C. 0.16
• D. 0.32

Answer 1

Answer: (C)

Remaining activity = 0.01 M after 24 h
Remaining activity
$\, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, $=Initial activity $\times\Bigg(\frac{1}{2}\Bigg)^n$
Used half-life time(n)=$\frac{Total time}{t_{1/2}}=\frac{24}{6}=4$
So $\, \, \, \, \, \, \, $0.01 = Initial activity $\times\Bigg(\frac{1}{2}\Bigg)^4$
Initial activity = 0.01 $\times$ 16 = 0.16