Question

State Avogadro’s Law.

Answer 1

A relation between number of moles and volume at constant temperature and pressure is given by V = K n, where ‘n’ is the number of moles of the gas and V is the volume of the gas.

Complete answer:
Avogadro’s law (volume-amount relationship)
This law was given by an Italian Scientist Amedeo Avogadro in the year 1811. He put forward a relation between the volume and number of molecules at constant temperature and pressure. It was experimentally found that the volume of a gas is directly proportional to the number of moles keeping temperature and pressure constant.I.e. V ∝ n (T and P constant)

Figure showing V ∝ n at T, P constant.
Where ‘n’ is the number of moles of the gas.
Or V = Kn
Or $\dfrac{V}{n} = K$
Where K is proportionality constant, now if two gases with volumes $V_1$ and $V_2$ and moles $n_1$ and $n_2$ at constant temperature and pressure are taken then $\dfrac{{{V_1}}}{{{n_1}}} = \dfrac{{{V_2}}}{{{n_2}}} = K$
It is evident from the above relation with if the volume of two gases is equal then number of moles is also equal
I.e. if $V_1$ = $V_2$
Then $n_1$ is also equal to $n_2$ ($n_1$ = $n_2$)
In this way Avogadro’s law states that the equal volume of all gases under the same condition of temperature and pressure contain equal number of moles or molecules

Note: As the ideal gas equation expresses the quantitative relation between the four variables that describe the state of a gas, therefore it is called the equation of state for gases.