Question

Suppose the elements X and Y combine to form two compounds XY₂ and X₃Y₂. When 0.1 mole of XY₂ weighs 10 g and 0.05 mole of X₃Y₂ weighs 9 g, the atomic weights of X and Y are _______ .
(A) 30, 20
(B) 40, 30
(C) 60, 40
(D) 20, 30

Answer 1

Answer:

(B) 40, 30

Explanation:

As per the question,

Let us consider that atomic weight of element X = x

And the atomic weight of element Y = y

According to given data of question,

When 0.1 mole of XY₂ weighs 10 g, that is,

$x + 2y = \frac{10}{0.1}$

$x + 2y = 100$

And when 0.05 mole of X₃Y₂ weighs 9 g, that is,

$3x + 2y = \frac{9}{0.05}$

$3x + 2y = 180$

Now we have two equations and two variables, on solving we get

2x = 80

⇒ x = 40

And,

∴ y = 30

Hence, the atomic weights of X and Y are 40 and 30 respectively.

Hence, the correct option is (B).