Question

what volume of air at STP containing 21% of oxygen by volume is required to completely burn sulphur S8 present in 200 gram of sample which contains 20% in 8 material which doesn't burn sulphur burns according to the reaction 1/8 S8 + O2 - SO2

Answer 1

We write down the equation for combustion :

1/8 S₈ + O₂ —> SO₂

The mole ratio is :

1 : 8

Meaning for every mole of Sulphur we need 8 moles of Oxygen gas.

The mass of sulphur that burns :

(80 / 100) × 200 = 160 g

Molar mass of S₈ = 32 × 8 = 256 gmol⁻¹

Moles of sulphur :

160 / 256 = 0.625 moles

Moles of Oxygen:

0.625 × 8 = 5moles

At stp molar gas volume is :

1 mole = 22.4 litres

Volume of oxygen is thus :

5 × 22.4 = 112 litres.

This is 21 % of volume of air.

100% volume of air is thus :

(100 / 21) × 112 = 533.33 Litres

Volume of air is thus :

533.33 Litres

Answer 2

533.33
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