The equation for the combustion of butane in oxygen is C4H10 + 13/2O2 --> 4CO2 + 5H2O The mole fraction of butane in a mixture of butane and oxygen with the minimum amount of oxygen required for complete combustion is... ?
Total moles of butane+oxygen = 7.5 Moles of butane = 1 The mole fraction will be moles of butane/moles of butane and oxyge so you do 1/7.5 which gives you 0.133