how many moles of carbon dioxide will be produced when 2.8 moles of oxygen react (consider the combustion of ethylene:

C2H4 + 3 Oxygen2 -->2CO2 +2H2Oxygen

3 answers

2.8/3 = x/2

working it as a ratio with the coefficents.
can you explain where did the 2 come from also the 3, i'm not an expert at chemistry and i need explaination to see how to do these problems.
thank you
The 2 and 3 are coefficients in the balanced equation for O2 and CO2