Question

If a pure compound is composed of X2y3
molecules and consists of 60% X by weight, what
is the atomic weight of Y in term of atomic weight
of X?​

Answer 1

Answer:

Atomic weight of Y = 4/9 times atomic weight of X

Explanation:

let the atomic weight of X be x and atomic weight of Y be y

Let the weight of the compound be 100 gm

Then weight of X will be 60% of 100 i.e. 60 gm and weight of Y will be 100-60 = 40 gm

Since one mole of X₂Y₃ consists of 2 moles of X and 3 moles of Y

Therefore, Using No. of moles  = weight/atomic weight

No. of moles of X = 60/x

no. of moles of Y = 40/y

60/x = 2                     .................................. (1)

40/y = 3                     .................................. (2)

Dividing (2) by (1)

$\frac{60/x}{40/y} =\frac{2}{3}$

or, $\frac{3y}{2x} =\frac{2}{3}$

or, y = (4/9)x