Question

Can I calculate the total pressure of a mixture of gases by adding together the partial pressures of the component gases?

Answer 1

You certainly can!

This is Dalton's Law of Partial Pressures.

In symbols, we write it as

`P_"total" = P_1 + P_2 + P_3 + …`, where the `P_i` are the partial pressures of the component gases.

EXAMPLE

The pressure of a mixture of nitrogen, carbon dioxide, and oxygen is 150 kPa. What is the partial pressure of oxygen if the partial pressures of the nitrogen and carbon dioxide are 100 kPa and 24 kPa, respectively?

Solution

`P_"total" = P_"N₂" + P_"CO₂" + P_"O₂"`

`P_"O₂" = P_"total" - P_"N₂" - P_"CO₂"` = 150 kPa – 100 kPa – 24 kPa = 26 kPa