a mixture of oxygen, nitrogen and hydrogen gases exerts a total pressure of 85 kpa at 0 degrees Celsius. The partial pressure of the oxygen is 20 kpa and the partial pressure of the nitrogen is 50 kpa. What is the partial pressure of the hydrogen gas in this mixtures?

15 kPa.

Explanation:

The total pressure of a mixture of gases can be defined as the sum of the pressures of each individual gas:

Ptotal = P1 + P2 + ... + Pn.

∴ Ptotal = P of oxygen + P of nitrogen + P of hydrogen.

∴ P of hydrogen = P total - (P of oxygen + P of nitrogen) = 85 kPa - (20 kPa + 50 kPa) = 15 kPa.