Air is a mixture of 78% nitrogen by mass, with the remainder being various other gases (mainly oxygen). What conversion factor can be made from the 78% value?

Question

How many grams of air contain 55.0 g of nitrogen?

Answer 1

One way to write this is for every 100 grams of air, there will be 78 grams of nitrogen. This can be expressed by a conversion factor by expressing this as a fraction:

78 grams nitrogen/ 100 grams of air = 0.78 grams of nitrogen/1 gram of air

To find how many grams of air contain 55.0 grams of nitrogen:

55.0 grams of nitrogen(1 gram of air/0.78 grams of nitrogen) = 70.5 grams of air