So in this equation, 3 oxygen will react with 1 ethylene.
then, you convert from 12.9 Liters to moles.
1 mole = 22.4 Liters of gas.
x moles = 12.9 liters
So, 22.4x = 12.9, which means that x = 12.9/22.4, and you get about 0.6, then you divide by 3 because you have 3 Oxygen, and you get about 0.2.
So, 0.2 moles of ethylene C2H4 can react with 12.9 liters of Oxygen Gas.
Hope this Helps :)
