CH4 + O2 = Co2 + H2O
Balanced equation
CH4 +2O2 = CO2 + 2H2O
2 moles of O2 is required for complete combustion of 1 mole CH4
Moles of CH4 = given mass / molar mass
4g/16g=1/4 moles
Moles of O2 Required for complete combustion of 1/4 moles =1/4×2=0.5 moles
At stp one mole of all gases = 22.4 litres
Thus 0.5 moles of O2 = 11.2 litres
Thus volume of O2 required for complete combustion of 4 g CH4 is 11.2 litres
Hope it helped you