# How can you calculate partial pressure?

Aug 20, 2016

By means of $\text{Dalton's Law of Partial Pressures}$.

#### Explanation:

In a gaseous mixture, the pressure exerted by a component, ${P}_{A}$, is the same as the pressure it would exert if it ALONE occupied the container. The total pressure is the sum of the individual partial pressures.

${P}_{\text{Total}}$ $=$ ${P}_{A} + {P}_{B} + {P}_{C} + {P}_{D} \ldots \ldots . .$

And if we assume ideality,

$=$ $\frac{{n}_{A} R T}{V} + \frac{{n}_{B} R T}{V} + \frac{{n}_{C} R T}{V} + \frac{{n}_{D} R T}{V} +$

Thus, ${P}_{\text{Total}}$ $=$ $\frac{R T}{V} \left\{{n}_{A} + {n}_{B} + {n}_{C} + {n}_{D} +\right\}$

And ${P}_{A}$ $=$ $\frac{R T}{V} \times {n}_{A} / \left\{{n}_{A} + {n}_{B} + {n}_{C} + {n}_{D} +\right\}$

Thus the partial pressure ${P}_{A} \propto \text{Mole fraction of Gas A}$, with the constant of proportionality $\frac{R T}{V}$.