Approximately how many moles of n2 are there in 200 moles of clean air?

Well assuming that in air, the composition of gases that are molecular nitrogen or N2 is about 80 percent, then the moles of N2 would be 80 % of 200 or 0.8 of 200 moles which would be 160, about 160 moles of N2 are present in 200 moles of clean air.