Question

a mixture of gases is prepared for laboratory experiments by combining 4.2 L of oxygen, 0.71 L of nitrogen, and 0.22 L of carbon dioxide. Determine the percentage of nitrogen in the mixture.

Answer 1

All at the same pressure and temperature? It matters.

Now percentage by mass?
Percentage by number molecule?

I suppose you want precentage by mass, but am not certain.

PercentN2= massN2/total mass

So assume sTP, as long as all are the same temp pressure, it doesn't matter.

massN2=.71/22.4 * 28 grams
massO2=4.2/22.4 * 32 grams
massCO2=.22/22.4 *44 grams

add to get toral, then figure percent.

Answer 2

What kind of percent? volume percent, mass percent, ---
If you want volume percent, then
%N2 = (volume N2/total volume)*100 = ?