In the context of two nonpolar, nonvolatile liquids, the relationship between solute concentration and the liquid-liquid equilibrium point can be described by Raoult's law.
Raoult's law states that the partial pressure of each component in an ideal mixture of liquids is directly proportional to its mole fraction in the solution. For nonpolar, nonvolatile liquids, we can assume ideal behavior in this scenario.
In the case of a solute dissolved in a liquid solvent, the solute concentration can be related to its mole fraction in the solution. The mole fraction of the solute is defined as the ratio of the moles of the solute to the total moles of the solution (solute and solvent combined).
At the liquid-liquid equilibrium point, the concentrations of the solute and solvent reach a balance where the rates of dissolution and separation of the two phases are equal. This equilibrium point can be influenced by the solute concentration.
If the solute concentration increases, the mole fraction of the solute in the solution will also increase. According to Raoult's law, this increase in solute mole fraction will result in an increase in its partial pressure. In turn, the partial pressure of the solvent component will decrease since the sum of the partial pressures must remain constant.
Therefore, an increase in solute concentration will generally lower the partial pressure of the solvent at the liquid-liquid equilibrium point. The exact effect on the equilibrium point will depend on the specific nature of the solute and solvent involved, as well as the temperature and pressure conditions.