Question

A small piece of commercial zinc weighing 10g is made to react with excess of dil.
H2SO4. The total volume of hydrogen gas liberated was found to be 3.1 litre at STP.
Determine the percentage purity of the zinc sample. Atomic mass of Zn = 65

*pls answer me if anybody can*

Answer 1

A small piece of commercial Zinc weighing 10g made to react with excess dil H₂SO₄. The total volume of Hydrogen gas liberated was found to be 3.1 litre at STP.

we have to determine the percentage purity of the zinc sample.

solution : Zn + H₂SO₄ (aq) ⇒ZnSO₄ (aq) + H₂ (g)

here it is clear that one mole of zinc produces 22.4 Litre of H₂ gas.( volume of one mole of H₂ at STP is 22.4 Litre )

here mass of commercial Zinc = 10g

molecular mass of Zn = 65 g/mol

so, no of moles of Zn = 10/65 = 0.154 mol

so, 0.154 mol of zinc will produce 22.4 × 0.154 = 3.4496 ≈ 3.45 Litre.

percentage purity of the given sample = experimental volume/theoretical volume × 100

= 3.1/3.45 × 100

= 89.85 % ≈ 90 %

Therefore percentage purity of the zinc sample is 90% .