Explain molecular weight of an element.

Molecular weight  of a substance is the relative weight which is the number of times a molecule of a substance is heavier than `1/12` of an atom of C-12.

It is the algebraic sum of atomic weight.

Molecular weight can be determined by following three methods:

• By diffusion method
• By vapour density method
• By avogadros method

By diffusion method:

This method is based on Grahams law of diffusion and is applicable only for gases.

`r_1/r_2=root()(M_2/M_1)`

Where r represents the rate of diffusion.

If equal volume of gas have diffused, then

`t_1/t_2=root()(M_2/M_1)`

By vapour density method:

Molecular weight of unknown gas=Vapour density * molecular weight of reference gas.

If reference gas is not specified then it is assumed to be Hydrogen.

By avogadros method:

Molecular weight=2 * V.D

where, V.D=Density of gas/ (Density of `H_2` gas under same tempera....

Molecular weight  of a substance is the relative weight which is the number of times a molecule of a substance is heavier than `1/12` of an atom of C-12.

It is the algebraic sum of atomic weight.

Molecular weight can be determined by following three methods:

• By diffusion method
• By vapour density method
• By avogadros method

By diffusion method:

This method is based on Grahams law of diffusion and is applicable only for gases.

`r_1/r_2=root()(M_2/M_1)`

Where r represents the rate of diffusion.

If equal volume of gas have diffused, then

`t_1/t_2=root()(M_2/M_1)`

By vapour density method:

Molecular weight of unknown gas=Vapour density * molecular weight of reference gas.

If reference gas is not specified then it is assumed to be Hydrogen.

By avogadros method:

Molecular weight=2 * V.D

where, V.D=Density of gas/ (Density of `H_2` gas under same temperature and pressure)

Under same temperature and pressure, equal volume of any gas contains same number of molecules or moles.