How many moles of ethylene can react with 12.9 l of oxygen gas at 1.2 atm in 297 k

The balanced reaction that describes reaction of ethylene and oxygen to produce carbon dioxide and water is expressed C2H2 (g) + 5/2 O2 (g) = 2cO2 (g) + h2O (g). We convert first the given data to moles thru PV=nRT. The number of moles of oxygen is 0.6349 moles. One mole of c2h2 reacts with 2.5 moles oxygen. The answer is 0.2539 moles c2h2.