Question

A sample has two isotopes $A^{150+}$ and B having masses 50 g and 30 g, respectively. A is radioactive and B is stable. A decays to A' by emitting $\alpha$- particles. The half-life of A is 2 h. Find the mass of the sample after 4 h and number of $\alpha$- particles emitted:

Answer 1

Mass of A after 4hr will be $\frac{M}{4}=\frac{50}{4}$

So, Mass of sample after 4hr $=\frac{50}{4}+30=12.5+30=42.5g$