Avogadro’s law (volume-amount relationship)

Avogadro’s law (volume-amount relationship)

Avogadro in 1811 put forward a relationship between volume of a gas to the number of molecules at constant temperature and pressure. This relationship is known as Avogadro’s law

 it states that at given temperature and pressure the volume of gas is directly proportional to the amount of gas. Mathematically, it can be expressed as

V α n -------------(1)

V= k₄ n   ---------(2)

Since n= given mas (m)/ molar mass(M)

So, V= k₄ m/M

Or   M= k₄ m/V ----------(3)        since [m/V =density(d)]

Therefore       

M= k₄ d ---------(4)

Eq. (4) gives relationship between molar mass and density of gas.

According to this principle, all gases containing equal amount of substance occupy the same volume at the same temperature and pressure. this means that one mole of each gas at standard temperature and pressure will have same volume. this is known as molar volume.