# What is Dalton law of partial pressure?

Jun 25, 2016

In a gaseous mixture, the pressure exerted by a particular component, is the same as the pressure it would exert if it alone occupied the container.

#### Explanation:

So in a gaseous mixture:

${P}_{\text{Total}}$ $=$ ${P}_{1} + {P}_{2} + {P}_{3} + \ldots \ldots \ldots \ldots {P}_{n}$

Where ${P}_{i}$ is the partial pressure of a component. But we can assume ideality, and thus,

${P}_{1} = \frac{{n}_{1} R T}{V}$, etc. since $V$ and $T$ are common to all the gases.

Since the total pressure is the sum of the partial pressures,

${P}_{\text{Total}} = \left({n}_{1} + {n}_{2.} \ldots \ldots . + {n}_{n}\right) \frac{R T}{V}$

And ${P}_{1}$ $=$ ${n}_{1} / \left({n}_{1} + {n}_{2} + {n}_{3} + \ldots . {n}_{n}\right) \times \frac{R T}{V}$

And so the partial pressure of a component is proportional to the mole fraction of that component. The law of course presupposes that the individual gases do not react with each other. Given that we are breathing such a mixture of gases right now at $1 \cdot a t m$, can you estimate the partial pressures of each component?