JEE Main & Advanced Chemistry States of Matter Avogadros Law

Avogadros Law

Category : JEE Main & Advanced

(1) According to this law, “Equal volumes of any two gases at the same temperature and pressure contain the same number of molecules.”


Thus, \[V\propto n\]              (at constant T and P)


or \[V=Kn\]            (where K is constant)


or \[\frac{{{V}_{1}}}{{{n}_{1}}}=\frac{{{V}_{2}}}{{{n}_{2}}}=.......=K\]


Example,                 \[\underset{1n\,litre}{\mathop{\underset{1\,litre}{\mathop{\underset{2\,litres}{\mathop{\underset{2\,volumes}{\mathop{\underset{2\,moles}{\mathop{2{{H}_{2}}(g)}}\,}}\,}}\,}}\,}}\,+\underset{1/2n\,litre}{\mathop{\underset{1/2\,litre}{\mathop{\underset{1\,litre}{\mathop{\underset{1\,volume}{\mathop{\underset{1\,mole}{\mathop{{{O}_{2}}(g)}}\,}}\,}}\,}}\,}}\,\xrightarrow{{}}\underset{1n\,litre}{\mathop{\underset{1\,litre}{\mathop{\underset{2\,litres}{\mathop{\underset{2\,volumes}{\mathop{\underset{2\,moles}{\mathop{2{{H}_{2}}O(g)}}\,}}\,}}\,}}\,}}\,\]


(2) One mole of any gas contains the same number of molecules (Avogadro's number \[=6.02\times {{10}^{23}}\]) and by this law must occupy the same volume at a given temperature and pressure. The volume of one mole of a gas is called molar volume, Vm which is 22.4 L \[mo{{l}^{-1}}\] at S.T.P. or N.T.P.


(3) This law can also express as, “The molar gas volume at a given temperature and pressure is a specific constant independent of the nature of the gas”.


Thus, \[{{V}_{m}}=\] specific constant \[=22.4\,L\,mo{{l}^{-1}}\] at S.T.P. or N.T.P.


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