Question

0.1 mole of AB2, has mass 10 g and 0.1 mole of A2B has mass 12.5 g. Thus, ratio of atomic weight of A to B is​

Answer 1

Given info : 0.1 mol of AB₂ has mass 10g and 0.1 mol of A₂B has mass 12.5g.

To find : the ratio of the atomic weight of A to B is ...

solution : ∵ 0.1 mol of AB₂ = 10g

∴ 1 mol of AB₂ = 100g

we know, mass of one mole of a compound is the sum of atomic mass of its contituent elements.

 molecular weight of AB₂ = atomic weight of A + 2 × atomic weight of B

⇒ 100g = A + 2B ...(1)

similarly, 0.1 mol of A₂B = 12.5 g

∴ 1 mol of A₂B = 125g

 molecular weight of A₂B = 2 × atomic weight of A + atomic weight of B

⇒ 125 = 2A + B ...(2)

from equations (1) and (2) we get, A = 25 and B = 75

therefore the ratio of atomic weight of A to B is 25/75 = 1/3