A sample of radioactive material has mass `m`, decay constant `lambda`, and molecular weight `M`. Avogadro constant `=N_(A)`. The initial activity of the sample is:

Options

A. `lambdam`
B. `(lambdaM)/(M)`
C. `(lambdamN_(A))/(M)`
D. `mN_(A)lambda`

Answer

C

Explanation

Activity = number of disintegration per unit time
Activity `=|(dN)/(dt)|=lambdaN`,
where N = the total number of nuclei.
Also, N = number of moles `xxN_(A)=((m)/(M)) N_(A)`.
`therefore" Initial activity "=(lambdamN_(A))/(M)`