JEE Main & Advanced Chemistry States of Matter / पदार्थ की अवस्थाएँ - गैस एवं द्रव Avogadros Law

(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, V_m 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.