Boyle's law:
It states "at a constant temperature (T), the pressure (P) of a given mass (or moles, n) of any gas varies inversely with the volume (V)".
Graham's law of diffusion states "under the same conditions of temperature and pressure, the rates of diffusion of different gases are inversely proportional to the square roots of their molecular masses or their densities."
Avogadro's Law : It states "equal volumes of any two gases at the same temperature and pressure contain the same number of molecules".