A certain radio isotope `._(Z)X^(A)` (half life `= 10 ` days) decays to give `._(Z-2)Y^(A-4)` . If `1.0 g` atom of `X` is kept in a sealed vessel, find the volume of helium accumulated at `STP` in `20` days ?

Explanation

`._(Z)^(A)X to ._(Z - 2)^(A - 4)Y + ._(2)^(4)He`
In two half lives, `(3)/(4)` of the isotopes `._(Z)^(A)X` has disintegrated.
`(3)/(4)g` atom helium has been formed `(3)/(4) g` atoms of `._(Z)^(A)A`
volume of 1g atoms of helium = 22400 ml
So, Volume of `(3)/(4) g` atom of helium `= (3)/(4) xx 22400 ml`
16800 ml.