A sample of radioactive material has mass m, decay constant λ, and molecular weight M. Avogadro constant = NA. The initial activity of the sample is
(a) λm
(b) λm/M
(c) λm NA/M
(d) mNAe λ
Correct Answer is: (c) λm NA/M
Activity = number of disintegrations per unit time
= |dN/dt| = λ. N, where N = the total number of nuclei.
Also, N = number of ***** x NA = (m/M) NA.
