# What is partial pressure and how is it used?

Jun 15, 2017

$\text{Partial pressure}$ is the pressure a gaseous component would exert.........

#### Explanation:

...........if it alone occupied the container. And the total pressure is the sum of the individual partial pressures.......

The total pressure is always the sum of the partial pressures.

The practical application of this is that the partial pressures in gaseous mixtures are always state functions of temperature.

i.e. ${P}_{\text{Total" = P_1+P_2+P_3...."etc}}$, where ${P}_{i}$ are the individual partial pressures. Of course, given ideal gas behaviour:

${P}_{\text{Total" = (n_1RT)/(V)+(n_2RT)/(V)+...."etc}}$,

${P}_{\text{Total}} = \frac{R T}{V} \left\{{n}_{1} + {n}_{2} + \ldots + {n}_{n}\right\}$, which is Dalton's law of Partial Pressures.

Because ${P}_{i} / {P}_{\text{Total}} = \frac{\frac{R T}{V} \left\{{n}_{1}\right\}}{\frac{R T}{V} \left\{{n}_{1} + {n}_{2} + \ldots + {n}_{n}\right\}}$

$= \frac{{n}_{1}}{\left\{{n}_{1} + {n}_{2} + \ldots + {n}_{n}\right\}}$

.........the partial pressure thus represents the mole fraction.