Question

Having a problem with these two... Which formula do I use? Thanks for your help! :)
1. A gas mixture contains 88 grams of oxygen gas, 88 grams of nitrogen gas, and 12 grams of nitrogen dioxide gas. What is the mole fraction of nitrogen dioxide in this mixture?
(Points : 3)
0.51

0.12

0.04

0.45



2. In the gas mixture containing 88 grams of oxygen gas, 88 grams of nitrogen gas, and 12 grams of nitrogen dioxide gas, what is the mole fraction of nitrogen gas?
(Points : 3)
0.12

0.45

0.51

0.81