Question

The activity of a sample of radioactive element ${}^{100}A$ is $6.02$ curie. Its decay constant is $3.7\times {10}^4{s}^{-1}$. The initial mass of the sample will be

• A. ${10}^{-14}g$
• B. ${10}^{-6}g$
• C. ${10}^{-15}g$
• D. ${10}^{-3}g$

Answer 1

The correct option is C ${10}^{-15}g$

Activity $=\lambda \times \frac{w}{At.wt.}\times 6.023\times {10}^{23}$
$6.02\times 3.7\times {10}^{10}=3.7\times {10}^4\times \frac{w}{100}\times 6.023\times {10}^{23}$
$w={10}^{-15}g$