Question

What volume of oxygen is required for the complete combustion of mixture of 5cm3 of CH4 & 5cm3 of C2H4?

Answer 1

lets write the reactions
CH4+ 2O2 --> CO2+2H2O So you need 2moles of O2 to burn 1 mole of CH4. as moles are proportional to volume at a given temperature you need 2*5=10cm^3 of O2 to burns 5 cm^3 of CH4
C2H6+ 3.5O2 --> 2CO2 + 3H2O with same thinking you need 3.5 moles of C2H4 to burn 1 mole of ethane so you need for 5cm^3 of C2H6 5*3.5=17.5 cm^3 of O2

to burn both, you need 10+17.5=27.5 cm^3 of O2