Question

An alloy of iron and carbon was treated with sulfuric acid, in which only the iron reacts.

if a sample of alloy weighing 2.358g gave home hydrogen which causes an explosion and generated 1.0368g of water, what is the percencentage of iron in the alloy?

(hint: Hydrogen can react with oxygen in the air and explode)

Answer 1

The chemical reactions involved in the given process are

Dissolution: 2Fe + 3H₂SO₄ Fe₂(SO₄)₃ +3H₂

Explosion: 2H₂ + O₂ 2H₂O

Number of moles of H₂O produced = weight/ molar mass = 1.0368 g / 18 .02 = 0.0575 mol

According to second equation, the mole ratio between H₂ and H₂O is 1:1

So, in the first step, 0.0575 mol of H₂ is produced.

From the stochiometry of first equation, the molar ratio between Fe and H₂ is 2:3.

So, amount of iron presnt in the sample = (2/3)* 0.0575 mol = 0.038 mol

Converting this into grams = 0.038 mol * 55.84 g/mol =  2.140 g

So, out of 2.358 g, 2.140g is iron.

The percentage of iron in the alloy = 90.75 %