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 `4h `and number of `alpha`-particles emitted.

Answer

`79g,1.5 xx10^(23)`

Explanation

After `4 h`, sample will contain ` 30g` of `B,12.5 g`, of `A` and `((146)/(150) xx 37.5)g` of `A'`
`:. Total mass =30 +12.5 +(146)/(150)xx37.5 =79 g`
Number of `alpha` particles emitted is
`(37.5)/(150) N_(A) =(1)/(4) N_(A) ~~1.5 xx10^(23)` .