The vapor pressure of water at room temperature is 23.8 mm Hg. The vapour pressure of an aqueous solution of sucrose with mole fraction 0.2 is equal to:

Explanation

The vapor pressure of a solution can be calculated using Raoult's law which states that the vapor pressure of a solution is directly proportional to the mole fraction of the solvent in the solution. Mathematically, it can be expressed as:P = X_solvent x P°_solventwhere P is the vapor pressure of the solution, X_solvent is the mole fraction of the solvent, and P°_solvent is the vapor pressure of the pure solvent.In this case, the solvent is water, and the mole fraction of sucrose is 0.2. Therefore, the mole fraction of water is:X_water = 1 - X_sucrose = 1 - 0.2 = 0.8The vapor pressure of pure water at room temperature is 23.8 mm Hg. Substituting these values in Raoult's law:P = X_water x P°_water = 0.8 * 23.8 = 19.04 mm HgTherefore, the vapor pressure of the aqueous solution of sucrose with mole fraction 0.2 is 19.04 mm Hg. Option A is the correct answer.