In Henry's Law for a dilute solute, which quantities are connected by the law?

• A. Temperature alone
• B. Total pressure, vapor-phase mole fraction, liquid-phase mole fraction, and Henry's constant
• C. Molar weight alone
• D. Surface tension alone

Answer: (B)

Henry's law for a dilute solute links the amount of solute in the liquid to how much of it appears in the gas phase at equilibrium, with a proportionality constant that depends on temperature. The law says the partial pressure of the solute in the vapor, p_i, is proportional to its mole fraction in the liquid, x_i, via p_i = H_i x_i, where H_i is Henry's constant. If the system has a total pressure P, the vapor-phase mole fraction is y_i = p_i / P, so you can write y_i = (H_i x_i) / P. This directly ties together the total pressure, the vapor-phase mole fraction, the liquid-phase mole fraction, and Henry's constant. Temperature affects Henry's constant, so the equilibrium relationship changes with temperature as well. Surface tension and molar weight aren’t part of this relationship.