Suppose elements `X` and `Y` combine to form two compounds `XY_(2)` and `X_(3)Y_(2)` when 0.1 mole of former weigh `10 g` while 0.05 mole of the latter weigh `9g`. What are the atomic weights of `X` and `Y`.

Options

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

Answer

A

Explanation

`XY_(2)`
0.1 mole weight=10g
`therefore1` mole weight=?=100 g mol wt
`X_(3)Y_(2)`
0.05 mole weight=9g
`therefore1` mole weight=?=`(9)/(0.05)=180g` mol. Wt
`thereforeFor` `XY_(2)`
`a+2b=100` . . . (1)
For `X_(3)Y_(2)`
`3a+2b=180` . . . (2)
equation (2)-(1)
2a=80
a=40
and b=30