A mixture of hydrogen and chlorine occupying 36 cm³ was exploded. On shaking it with water, 4 cm³ of hydrogen was left behind. Find the composition of the mixture.

What volume of air (containing 20% O₂ by volume) will be required to burn completely 10 cm³ each of methane and acetylene?

CH₄ + 2O₂ ⟶ CO₂ + 2H₂O

2C₂H₂ + 5O₂ ⟶ 4CO₂ + 2H₂O

200 cm³ of CO₂ is collected at STP when a mixture of acetylene and oxygen is ignited. Calculate the volume of acetylene and oxygen at STP in the original mixture.

2C₂H₂ (g) + 5O₂ (g) ⟶ 4CO₂ (g)+ 2H₂O (g)

You have collected (a) 2 litres of CO₂ (b) 3 litres of chlorine (c) 5 litres of hydrogen (d) 4 litres of nitrogen and (e) 1 litres of SO₂, under similar conditions of temperature and pressure. Which gas sample will have:

(a) the greatest number of molecules, and

(b) the least number of molecules?

Justify your answers.