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Gas lawsFrom Wikipedia, the free encyclopedia

This article outlines the historical development of the laws describing ideal gases. For a detaileddescription of the ideal gas laws and their further development seeideal gas law.

The gas lawswere developed at the end of the 18th century, when scientists began to realize thatrelationships between the pressure, volumeand temperatureof a sample ofgascould be obtainedwhich would hold to a good approximation for all gases !ases behave in a similar way over a widevariety of conditions because they all have moleculeswhich are widely spaced, and the e"uation ofstatefor anideal gasis derived from kinetic theory The earlier gas laws are now considered asspecial cases of the ideal gas e"uation,with one or more of the variables held constant

Contents

#hide$

1%oyle&s 'aw

()harles& 'aw

*!ay+'ussac&s 'aw

-vogadro&s 'aw

.)ombined and /deal !as 'aws

0ther gas laws

23eferences

Boyle's Law#edit$Main article:Boyle's Law

%oyle&s 'aw, published in 100(, states that, at constant temperature, the product of the pressure andvolume of a given mass of anideal gasin a closed system is always constant /t can be verifiedexperimentally using a pressure gauge and a variable volume container /t can also be derived fromthe kinetic theory of gases4 if a container, with a fixed number of molecules inside, is reduced involume, more molecules will strike a given area of the sides of the container per unit time, causing agreater pressure

-s a mathematical e"uation, %oyle&s 'aw is written as either4

, or

, or

where Pis the pressure, and is the volume of a gas, and !1is the constant in thise"uation 5and is not the same as the proportionality constants in the other e"uationsbelow6 The statement of %oyle &s law is as follows4

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The volume of a given mass of a gas is inversely related to the pressure exerted on it ata given temperature and given number of moles

Charles' Law#edit$

Main article: "harles's Law)harles& 'aw, or the law of volumes, was found in 1282 by 7ac"ues )harles /t statesthat, for a given mass of an ideal gas at constant pressure, the volume is directlyproportional to its absolute temperature,assuming in a closed system

-s a mathematical e"uation, )harles& 'aw is written as either4

, or

, or

where is the volume of a gas, Tis the absolute temperature and !(is aproportionality constant 5which is not the same as the proportionality

constants in the other e"uations in this article6

Gay-Lussac's Law#edit$Main article: #ay$Lussac's Law

!ay+'ussac&s 'aw, or the ressure 'aw, was found by 7oseph 'ouis !ay+'ussacin 189: /t states that, for a given mass and constant volume of anideal gas, the pressure exerted on the sides of its container is directlyproportional to its absolute temperature

-s a mathematical e"uation, !ay+'ussac&s 'aw is written as either4

, or

, or

where Pis the pressure, Tis the absolute temperature,and !*is another proportionality constant

Avogadro's Law#edit$Main article:%vogadro's Law

-vogadro&s 'aw states that the volume occupied by an idealgas is directly proportional to the number of molecules of thegas present in the container This gives rise to the molar

volumeof a gas, which at ;Tis (( dm*5orlitres6 Therelation is given by

where nis e"ual to the number of molecules of gas 5or thenumber of moles of gas6

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Combined and Ideal Gas Laws#edit$Main article:&deal #as Law

The )ombined !as 'awor !eneral !as '6?5mol>=6

-n e"uivalent formulationof this 'aw is4

where

pis the pressure

is the volume

(is the number of gas molecules

!is the %oltzmann constant51*81@19A(*7>=A1in ;/ units6

Tis the absolute temperature

T

hesee"uati

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onsare

exactonlyfora

nidealgas,wh

ichneglectsva

riousinter

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molecu

lareffects5see

realgas6Bowe

ver,theidealga

slaw

isag

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oodapp

roximationform

ostgasesunde

rmoderatepres

sureandte

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mperat

ure

Thislaw

hasthefollowin

gimportantconse"uences4

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1 /ftemperature

andpressurearekeptconstant,the

nthevolumeofthegasisdirect

lyproportionaltothenumberofmolec

ulesofgas

( /fthete

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mperatureand

volumeremainconstant,thenthe

pressureofthegaschangesis

directlyproportionaltothenumberof

moleculesofgaspre

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sent

* /fthenu

mberofgasmoleculesandthetemperatureremainconstant,the

nthepressureisinverselyproportional

tothevolume

/fthete

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mperaturechan

gesandthenumberofgasmolec

ulesarekeptconstant,theneit

herpressureorvolume5orboth6willch

angeindirectproportion

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tothetemperatur

e

Otherga

slaws#edit$

!

raham&slaw

statesth

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atther

ateatwhichgas

moleculesdiff

useisinversel

yproportio

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naltot

hes"uarerooto

fitsdensity)o

mbinedwith

-vog

adro&slaw

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5ies

incee"ualvolu

meshavee"ual

numberofmolec

ules6this

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isthes

ameasbeinginv

erselypropor

tionaltotheroo

tofthemol

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ecular

weight

C

alton&slawofpartia

lpressuressta

testhatth

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epress

ureofamixture

ofgasessimpl

yisthesum

oft

hepartialp

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ressur

esoftheindivi

dualcomponen

tsCalton&s'aw

isasfollo

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ws4

,

OR

wherePTotalisthetotalpressure oftheatmos

phere,P!asisthepressure ofthegasmixture intheatmosphere,

and PB(

is thewaterpressure atthattemperature

Be

nry&slaw

statesthat4

%t constant temperature) the amount of a given gas dissolved in a given type and volume ofli*uid is directly proportional to thepartial pressureof that gas in e*uilibrium with that li*uid.

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Refers#edit$

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