This is true for ideal gasses. not for the gasses come accross. A better solution taking the air molecules as finite size is given by Vander Waal eqn:
(P + na/V²)(V - nb) = nRT for n mole of gas. a,b are called Van Dar Waals constants. They are different for different gasses. This equation is not emperical, rather thermodynacially proven.