When `2g` of gas `A` is introduced into an evacuated flask kept at `25^(@)C` the pressure is found to be `1atm`. If `3g` of another gas `B` is then added to the same flask the total pressure becomes `1.5 atm` .Find the ratio of molar mass of `A` to molar mass of `B` .

Explanation

Let `M_(A)` and `M_(B)` be the molecular of A and B .
Using PV = nRT for A, we get
`I= ((2)/( M_(A)), RT)/( v)` …..(i)
and using Dalton's Law`: P_("Total") = ((n_(A) + n_(B))RT)/(v) rArr 1.5 = (((2)/( M_(A))+ (3)/( M_(B)))RT)/(V) `.....(ii)
Solving (i) and (ii) , we get `(M_(A))/( M_(B))=(1)/(3)`