Question

How does Dalton’s law of partial pressure work?

Answer 1

This law applies when there is a mixture of gases present in a container. We know gases are compressible and when we apply pressure on gases they compress and can change in liquid state. In a mixture of gases a question arises that what is the total pressure of that mixture so Dalton gave a law on behalf of this.

Complete step-by-step answer:
Suppose we have a container having partition in it containing two types of gases let’s say gas A and gas B. When we take their pressure, the gas possesses its individual pressure so pressure of gas A is ${p_A}$ and pressure of gas B is ${p_B}$ .

Now let’s say we remove the partition from the container, now the gases get mixed and the total pressure of the container is equal to the sum of individual pressure of gases. Now we can write the total pressure as this ${p_T} = \,{p_A}\, + \,{p_B}$ we have taken the sum as of two gases A and B, but it is not necessary that there may be two gases always present in the container.

Let’s say there are a number of gases like we have in the atmosphere, so according to Dalton’s law we can write that the total pressure of the gas mixture is equal to the sum of pressure of each gas present in the container.
${p_T} = \,{p_A}\, + \,{p_B} + \,\,{p_C}\, + \,{p_D} + \,.........$

These A, B,C and D are all the gases present in the container; it may be carbon dioxide, methane oxygen etc.

Note: Dalton’s law is a law which is based on gases or we can say that it is applicable to gases only and not on the solids or liquids. Individual pressure is equals to the mole fraction multiplied with the total pressure, so if we write it for gas A then the expression is just like this, ${p_A} = \,{x_A}\,{p_T}$ here ${p_T}$ is the total pressure and ${x_A}$ is the mole fraction of that gas.