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

(i) `X+2Y rarr X_(3)Y_(2), 0.05` mol of `X_(3)Y_(2) = 9g, " "1 " mol of " X_(3)Y_(2) = 100 g`
(ii) `3X + 2Y rarr X_(3)Y_(2), " 0.05 mol of " X_(3)Y_(2) = 9g , " 1 mol of " X_(3)Y_(2) = (9)/(0.05) = 180 g`
`:. {:("X+2Y" = 100),(3X + 2Y = 180):}]{:("MW of "XY_(2) = 100),("MW of "X_(2)Y_(3) = 180):}`
Solve for X and Y
X = 40 g
Y = 30 g