Question

Nitric oxide (NO) reacts with oxygen gas to form nitrogen dioxide (NO2), a dark brown gas:
2NO + O2 -> 2NO2
In one experiment, 0.845 mol of NO is mixed with 0.491 mol of O2. Calculate also the number of moles of NO2 produced.

Answer 1

You're given amounts of both reactants, so you need to first find which one is limiting. To do that, divide the moles of reactant by the coefficient of that reactant in the equation. The smallest number you end up with is your limiting reactant.

NO: 0.845/2 = 0.4225
O2: 0.491/1 = 0.491

NO has the lower number, so that's the limiting reactant. According to the chemical reaction, for every 2 moles of NO reacted, 2 moles of NO2 are produced. In other words, they react in a 2:2 or more simply 1:1 ratio. However much NO you start with equals the amount of NO2 you finish with, so you end up with 0.845 mol of NO2.

Answer 2

Thanks!