I study in class 12, and have a doubt in vapour pressure that my school teacher and my friends are not able to clarify.
My doubt is the reason why the partial vapour pressure of each individual component of a solution is not equal to their respective standard vapour pressures($P°$)?
My reasoning is that consider you have a pure liquid A in a closed container, the vapour pressure of it shall be equal to $P°_A$. Now when you add another volatile liquid B, a solution should be formed; however, the equilibrium of the reaction
$$\ce{A_{liq} <=> A_{vap}}$$ should not be affected since the concentration of reactants and products remains the same since B is different from A. Eventually, the reaction of B must also reach equilibrium, independently, and thus the partial pressure of B must be equal to $P°_B$ .
However, this does not seem to be the case. Could someone please help in clarifying my doubt through the viewpoint of equilibrium(Mathematically if possible) and not the standard explanation that the surface of the solvent get's blocked by the particles of the solute, hence the vapour pressure reduces.
Regards, Arun