how many moles of o2 are required to react completely with 3.2 moles of c2h6?
Multiply the given moles C2H6 by the mole ratio between O2 and C2H6 in the balanced equation, so that moles C2H6 cancel, leaving moles O2. ~11 moles of O2 are required to react completely with 3.2 moles of C2H6.