# Dalton's law

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Dalton's law

In chemistry and physics, Dalton's law (also called Dalton's law of partial pressures) states that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture. This empirical law was observed by John Dalton in 1801 and is related to the ideal gas laws.

Mathematically, the pressure of a mixture of gases can be defined as the summation

$P_{total} = \sum_{i=1} ^ n {p_i}$       or      $P_{total} = p_1 +p_2 + \cdots + p_n$

where $p_{1},\ p_{2},\dots,\ p_{n}$ represent the partial pressure of each component.

It is assumed that the gases do not react with each other.

$\ p_{i} =P_{total}y_i$

where $y_i\ =$ the mole fraction of the i-th component in the total mixture of n components .

The relationship below provides a way to determine the volume based concentration of any individual gaseous component.

$P_i =\frac{P_{total}C_i}{1,000,000}$

where: $C_i\ =$ is the concentration of the ith component expressed in ppm.

Dalton's law is not exactly followed by real gases. Those deviations are considerably large at high pressures. In such conditions, the volume occupied by the molecules can become significant compared to the free space between them. Moreover, the short average distances between molecules raises the intensity of intermolecular forces between gas molecules enough to substantially change the pressure exerted by them. Neither of those effects are considered by the ideal gas model.

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### Look at other dictionaries:

• Dalton's law — Law Law (l[add]), n. [OE. lawe, laghe, AS. lagu, from the root of E. lie: akin to OS. lag, Icel. l[ o]g, Sw. lag, Dan. lov; cf. L. lex, E. legal. A law is that which is laid, set, or fixed; like statute, fr. L. statuere to make to stand. See… …   The Collaborative International Dictionary of English

• Dalton's law — n LAW OF PARTIAL PRESSURES * * * Dal·ton s law (dawlґtənz) [John Dalton, English chemist and physicist, 1766â€“1844, the founder of the atomic theory] see under law …   Medical dictionary

• Dalton's law — Physics, Chem. the law that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the gases of the mixture. Also called Dalton s law of partial pressures, law of partial pressures. [named after J.… …   Universalium

• Dalton's Law — Multiple Mul ti*ple, a. [Cf. F. multiple, and E. quadruple, and multiply.] Containing more than once, or more than one; consisting of more than one; manifold; repeated many times; having several, or many, parts. [1913 Webster] {Law of multiple… …   The Collaborative International Dictionary of English

• Dalton's law — n. Dalton s law of partial pressure, physical law that says that the total pressure used by a gaseous mixture equals to the sum of the partial pressures of gases if they alone were present (Law named after the famous English physicist John… …   English contemporary dictionary

• Dalton's law — noun 1. (chemistry) law stating that when two elements can combine to form more than one compound the amounts of one of them that combines with a fixed amount of the other will exhibit a simple multiple relation • Syn: ↑law of multiple… …   Useful english dictionary

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