30ml of a mixture of CH₄ and C₂H₄ were burnt in excess of air. The volume of CO₂ produced after explosion and cooling was 40ml. The composition of CH₄ in the mixture is

Volume of gaseous mixture of CH₄ and C₂H₄         = 30ml
Volume of CO₂ liberated due to the combustion mixture   = 40ml
Let the volume of C₂H₄  in the mixture be V ml then the Volume of CH₄ in the mixture will be (30-V)ml
A) C₂H₄ + 3 O₂ $\to$2 CO₂ + 2H₂O_(l) 

From stoichiometry,

 CO₂ obtained from “V” ml of Ethene = 2V ml

CH₄ + 2 O₂ $\to$CO₂ + 2H₂O_(l)

From stoichiometry,

 CO₂ obtained from (30 - V) ml of methane = (30 - V) ml

Total volume of CO₂ formed = 2V+(30-V) = (30 + V)
Given 30 + V = 40
                 V = 10ml