Assuming that the air in a room consists of 78% nitrogen molecules and 22%

Assuming that the air in a room consists of 78% nitrogen molecules and 22% oxygen molecules, prove that the average mass of an air molecule is approximately 29 amu.

To answer this question, it is necessary to determine the molar mass of nitrogen and oxygen molecules.

Since the oxygen molecule is diatomic, therefore, its molar mass is:

2 * 16 = 32 amu

Since the nitrogen molecule is diatomic, therefore, its molar mass is:

2 * 14 = 28 amu

Now, since the percentage of each molecule in the air is known, you can answer the question in the following way:

32 * 0.22 + 28 * 0.78 = 21.84 + 7.04 = 28.88 amu

Rounding this number to integers you get 29 amu.