道尔顿分压定律

在组分之间不发生化学反应的前提下，理想气体混合物的压强等于各组分的分压之总和。数学描述为： P_(total)=p₁+p₂+⋯ +pₙ

其中 p₁,p₂,pₙ 为每一个组分的分压。

结合波义耳定律和阿伏伽德罗定律，可以推知理想气体各组分的分压之比等于其摩尔组分之比，即 （公式略）

其中 m₁,m₂,mₙ 为每一个组分的摩尔数。

需要注意的是，实际气体并不严格遵从道尔顿分压定律，在高压情况下尤其如此。当压强很高时，分子所占的体积和分子之间的空隙具有可比性；同时，更短的分子间距离使得分子间作用力增强，从而会改变各组分的分压。这两点在道尔顿定律中并没有体现。

Dalton's law (also called Dalton's law of partial pressures) states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. This empirical law was observed by John Dalton in 1801 and published in 1802. Dalton's law is related to the ideal gas laws.

Formula

Mathematically, the pressure of a mixture of non-reactive gases can be defined as the summation: p_(total)=∑ ᵢ₌₁ⁿpᵢ=p₁+p₂+p₃+⋯ +pₙ

where p1, p2,..., pn represent the partial pressures of each component. pᵢ=p_(total)xᵢ

where xi is the mole fraction of the ith component in the total mixture of n components.

Volume-based concentration

The relationship below provides a way to determine the volume-based concentration of any individual gaseous component pᵢ=p_(total)cᵢ

where ci is the concentration of component i.

Dalton's law is not strictly followed by real gases, with the deviation increasing with pressure. Under such conditions, the volume occupied by the molecules becomes significant compared to the free space between them. In particular, the short average distances between molecules increases intermolecular forces between gas molecules enough to substantially change the pressure exerted by them, an effect not included in the ideal gas model.