Write the overall reaction for the combustion of butane (C4H10) with 120% theoretical air. Solution Percentage of Carbon in C4H10 = 48*100/(48+10) % = 82.76% Percentage of Hydrogen = 100 - 82.76 = 17.24 % Theretical Air required = 4.31(2.67C + 8H) = 15.468 kg of air /kg of fuel Actual Air Supplied = 1.2* 15.468 = 18.562 kg/kg of fuel Now since excess air is supplied there is no formation of carbon monoxide C4H10 + 7.15O2 -----> 4CO2 + 5H2O + 0.65O2.