Suppose the elements X and Y combine to form two compounds of `XY_(2) and X_(3)Y_(2)`. When 0.1 mole of `XY_(2)` weighs 10 g and 0.05 mole of `X_(3)Y_(2)` weighs 9 g , what are tha atomic masses of X and Y ?

Explanation

Suppose atomic masses of X and Y are x and y respectively.
Molar mass of `XY_(2)=x+2y`
But 0.1 mol of `XY_(2)` weighs = 10 g
`therefore" Molar mass of"XY_(2)=100" "therefore" "x+2y=100" …(i)"`
But 0.05 mol of `X_(3)Y_(2)` weigh = 9 g
`therefore" Molar mass of "X_(3)Y_(2)=(9)/(0.05)=180" "therefore" "3x+2y=180" ...(ii)"`
Subtracting eqn. (i) from eqn. (ii), we get
`{:(,2x=80,or,x=40,,),("Substituting in eq. (i),",40+2y=100,or,2y=60,or,y=30):}`