Question

element x and y combine to form two compounds xy and x2y . find the atomic weight of x and y, if the weight of 0.1 moles of xy is 10g and 0.05 moles of x2y is 9g.​

Answer 1

$\boxed{Final \: Answer :-}$

80 ; 20

$\boxed{According \: to \: Question :-}$

• Element Y and X combine to form two compounds XY and $X_2 Y$

• 0.1 moles of XY is 10g
• 0.05 moles of $X_2 Y$ is 9g

$\boxed{To \: Find :-}$

the atomic weight of X and Y

$\boxed{Formula \: Used :-}$

$Number \: of \: moles =\frac{mass \: in \: gramss}{atomic \: mass \: of \: solution }$

$n=\frac{M}{m}$

$\boxed {Solution :-}$

lets be the atomic mass of element X ⇒ x

and

atomic mass of element Y ⇒ y

molecular mass of $XY$ →  x+y

molecular mass of $X_2 Y$ → 2x+y

$0.1=\frac{10}{x+y}$ (i) ⇒ $0.1x+0.1y=10$ ⇒$0.1x+0.1y -10=0$

$0.05=\frac{9}{2x+y}$ (ii) ⇒ $0.1x +0.5y =9$⇒$0.1x +0.05y -9 =0$

subtracting eq ii from eq ii

$0.1x+0.1y -10 -(0.1x +0.05y -9)=0\\0.1x+0.1y -10 -0.1x -0.05y +9=0\\0.05y-1=0\\0.05y=1\\y=\frac{1}{0.05} \\y=20$

now put y=20 in eq i

$0.1x+0.1(20)=10\\0.1x+2=10\\0.1x=10-2\\x=\frac{8}{0.1} \\x=80$

hence the atomic weight of x and y will be 80 and 20

Answer 2

Given: Elements x and y combine to form two compounds xy and x₂y. The weight of 0.1 moles of xy is 10 g and 0.05 moles of x₂y is 9 g.​

To find: The atomic weight of x and y.

Solution:

• The reaction given in the question can be represented as follows,

        $X + Y -> XY + X_{2}Y$

• On balancing,

        $3X + 2Y -> XY + X_{2}Y$

• Now, if 0.1 moles of xy is 10 g, then the weight of 1 mole of xy would be,

        $\frac{10 * 1}{0.1} = 100 g$

• Hence, the sum of the weights of x and y is 100 g.

       $X + Y = 100$

• If 0.05 moles of x₂y is 9 g, then the weight of 1 mole of x₂y would be,

        $\frac{9 * 1}{0.05} = 180g$

• So, the sum of twice the weight of x and the mass of y is 180 g.

        $2X + Y = 180$

• Two equations are obtained, and on solving them simultaneously, the weights of x and y are found to be

        $X = 80 g$

        $Y = 20 g$

Therefore, the atomic weight of x and y is 80 g and 20 g, respectively.