Question

How valency of metal in Z2O3 is 3?

Answer 1

by cross multiplication
we get valency of oxygen is 2
and valency of z is 3

Answer 2

Given,
Metal oxide has the formula Z2O3
Valency of the metal in Z2O3 = 3
Z2O3 + 3H2 → 2Z + 3H2O
As 0.16 g of Z2O3 reacts with H2 = 6 mg = 0.006 g
So, 1 g of H2 react with 0.16/0.006 = 26.67 g of Z2O3
Hence,
Equivalent weight of Z2O3 = 26.67

Equivalent weight of Z + Equivalent weight of O = E + 8 = 26.67

Therefore,
Equivalent weight of Z = 26.67 - 8 = 18.67

Hence,
Atomic weight of Z = 18.67 x 3 = 56.01