Question

Suppose two elements `X` and `Y` combine to form two compiounds `XY_(2)` and `X_(2)Y_(3)` when `0.05` mole of `XY_(2)` weighs `5g` while `3.011xx10^(23)` molecules of `X_(2)Y_(3)` weighs `85g`. The atomic masses of `X` and `Y` are respectively.
A. `20,30`
B. `30,40`
C. `35,30`
D. `80,60`

Answer 1

Correct Answer - 3
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`