Question

Suppose the elements X and Y combine to form two compounds `XY_(2)` and `X_(3)Y_(2)`. When 0.1 mole of `XY_(2)` weights 10 g and 0.05 mole of `X_(3)Y_(2)` weights 9 g, the atomic weight of X and Y are
A. 30, 20
B. 40, 30
C. 60, 40
D. 20, 30

Answer 1

Correct Answer - B
For `XY_(2)" "n=W/M`
`0.1=10/(X+2Y)=X+2Y=100` ...(i)
For `X_(3)Y_(2)" "n=W/M`
`0.05=9/(3X+2Y)=3X+2Y=180` ...(ii)
From (i) and (ii)
`2X=80`
`X=40 and 2Y=100-40=60`
`=Y=30`