Question

A sample of radioactive material has a mass m, decay constant λ and molecular weight M. If $N_A$ is Avogadro's number, the initial activity of the sample is:

• A. λm
• B. λm/M
• C. λmN_A/M
• D. mMe²

Answer 1

The correct option is C

λmN_A/M

$\text{Initial activity}=\lambda N=\lambda \left[\frac{m}{M}\right]N_A=\left(\frac{\lambda m}{M}\right)N_A$