Question

One mole of a metallic oxide reacts with one mole of hydrogen to produce two moles of the pure metal

and one mole of water. 5.00 g of the metallic oxide produces 2.32 g of the metal. What is the metallic
oxide? (Use molar masses)

Answer 1

The metallic oxide is Li₂O

Step-by-step explanation:

Let the metallic oxide be M₂O

Thus;

M₂O + H₂ = 2M + H₂O

Molar mass of M₂O = (2x + 16)

We assume Molar mass of M to be x.

We are told that 5.00 g of the metallic oxide produces 2.32 g of the metal.

By proportion, we can write the following;

5g of M₂O × (1 mole of M₂O/(2x + 16)) × (2 moles of M/1 mole of M₂O) = 2.32 g of M × 1 mole of M/x g of M

This cancels out to give us;

10/(2x + 16) = 2.32/x

Cross multiply to get;

10x = 2.32(2x + 16)

10x = 4.64x + 37.12

10x - 4.64x = 37.12

5.36x = 37.12

x = 37.12/5.36

x = 6.925 g/mol

The metal with a molar mass closest to this value of x is Lithium which has a molar mass of 6.94 g/mol

Thus the metal is Lithium and as such the metallic oxide is Li₂O