Q2 of 24 Page 166

How will you establish the relation between vapour density and molecular mass of a gas by applying Avogadro’s law?

Relative Molecular Mass: It is defined as the ratio of the mass of 1 molecule of the gas or vapour to the mass of 1 atom of hydrogen.



Vapour Density (V.D): It is defined as the ratio of the mass of a certain volume of the gas or vapour to the mass of the same volume of hydrogen at the same temperature and pressure.



Applying Avogadro’s Law,



Since hydrogen is diatomic,




2 x V.D = relative molecular mass of a gas or vapour


2 x Vapour density = Relative molecular mass


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