Suppose two elements X and Y combine to from two compounds `XY_(2)` and `X_(2)Y_(3)` . 0.05 mole of `XY_(2)` weighs 5 g while `3.011xx10^(23)` molecular of `X_(2)Y_(3)` weigh 85 g . The atomic masses of X and Y are respectively :

Options

A. `20,30`
B. `30,40`
C. 40,30`
D. `80,60`

Answer

3

Explanation

Molecular weight of `XY_(2)=(5)/(0.05)=100`
Molecular weight of `X_(2)Y_(3)=(85)/(3.011xx10^(23))xxN_(A)=170`
Let molar mass of `X` and `Y` are a and b respectively
`:. " " a+2b=100`
`3a+2b=170,`
`a=35`
`b=30`