Question

Veeni thermally decomposed 90 g of potassium chlorate of 60% purity. The total gas produced was allowed to react with hydrogen that was prepared by passing steam over hot magnesium metal. Calculate the amount of magnesium required to produce just sufficient hydrogen for completion of the reaction.

Answer 1

Given KCIO₃ = 90 gm (60% purity)

Oxygen gas will be produced on decomposition of KCIO₃.

2 moles of KCIO₃ gives 3 moles O₂ 

∴ 0.44 moles of KCIO₃ will give = 3/2 x 0.44 moles of O₂ = 0.66 moles of O₂ 

When O₂ reacts with H₂ , it gives H₂O.

O₂ + 2H₂ → 2H₂O

One mole of oxygen require 2 moles of H₂.

∴ 0.66 mole O₂ required = 0.66 × 2 = 1.32 mole of H₂ required

For the production of H₂ gas steam is passed over hot Mg metal.

1 mole of H₂ will be obtained from 24 gm Mg.

∴ 1.32 mole of H₂ will require = 24 × 1.32 gm = 31. 68 gm Mg.

∴ 31.68 gm Mg metal is required.