Dalton's law (also called Dalton's law of partial pressures) states that in a mixture of non-reacting gases, the total
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
exerted is equal to the sum of the
partial pressure
In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal g ...
s of the individual gases.
This
empirical
Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences and ...
law was observed by
John Dalton
John Dalton (; 5 or 6 September 1766 – 27 July 1844) was an English chemist, physicist and meteorologist. He is best known for introducing the atomic theory into chemistry, and for his research into Color blindness, colour blindness, which ...
in 1801 and published in 1802.
[J. Dalton (1802)]
"Essay IV. On the expansion of elastic fluids by heat,"
''Memoirs of the Literary and Philosophical Society of Manchester'', vol. 5, pt. 2, pages 595–602; see page 600. Dalton's law is related to the
ideal
Ideal may refer to:
Philosophy
* Ideal (ethics), values that one actively pursues as goals
* Platonic ideal, a philosophical idea of trueness of form, associated with Plato
Mathematics
* Ideal (ring theory), special subsets of a ring considered ...
gas laws.
Formula
Mathematically, the pressure of a mixture of non-
reactive gases can be defined as the summation:
where ''p''
1, ''p''
2, ..., ''p
n'' represent the partial pressures of each component.
where ''x
i'' is the
mole fraction of the ''i''th 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
where ''c
i'' 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.
See also
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References
{{authority control
Gas laws
Physical chemistry
Engineering thermodynamics
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