Dalton's Law Of Partial Pressures
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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 and eve ...
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 is evidence obtained through sense experience or experimental procedure. It is of central importance to the sciences and plays a role in various other fields, like epistemology and law. There is no general agreement on how t ...
law was observed by
John Dalton John Dalton (; 5 or 6 September 1766 – 27 July 1844) was an English chemist, physicist and meteorologist. He introduced the atomic theory into chemistry. He also researched Color blindness, colour blindness; as a result, the umbrella term ...
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 The laws describing the behaviour of gases under fixed pressure, volume, amount of gas, and absolute temperature conditions are called gas laws. The basic gas laws were discovered by the end of the 18th century when scientists found out that re ...
.


Formula

Mathematically, the pressure of a mixture of non-
reactive Reactive may refer to: *Generally, capable of having a reaction (disambiguation) *An adjective abbreviation denoting a bowling ball coverstock made of reactive resin *Reactivity (chemistry) *Reactive mind *Reactive programming See also *Reactanc ...
gases can be defined as the summation: p_\text = \sum_^n p_i = p_1+p_2+p_3+\cdots+p_n where , , ..., represent the partial pressures of each component. p_ = p_\text x_i where is the
mole fraction In chemistry, the mole fraction or molar fraction, also called mole proportion or molar proportion, is a quantity defined as the ratio between the amount of a constituent substance, ''ni'' (expressed in unit of moles, symbol mol), and the to ...
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 p_i = p_\text c_i 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 force An intermolecular force (IMF; also secondary force) is the force that mediates interaction between molecules, including the electromagnetic forces of attraction or repulsion which act between atoms and other types of neighbouring particles (e.g. ...
s between gas molecules enough to substantially change the pressure exerted by them, an effect not included in the ideal gas model.


See also

* * * * * * * * *


References

{{authority control Gas laws Physical chemistry Engineering thermodynamics de:Partialdruck#Dalton-Gesetz et:Daltoni seadus