Density of dry air containing only ( N₂ ) and ( O₂ ) is ( 1.15 , g/L ) at ( 740 , mm ) of Hg and ( 300 , K ). What is the composition of ( N₂ ) by mass in the air?
a. ( 28.0% )
b. ( 72.0% )
c. ( 78.0% )
d. ( 22.0% )