What is the mole fraction of a nonelectrolyte in a aqueous above which the vapor pressure of water is 745 mm hg at 100C

Rault's law: the vapor pressure of a non-volatile solution is equal to the vapor pressure of the solvent times the molar fraction of the solvent (at the same temperature).

Pv water in the solution = X water * Pv of pure water

745 mmHg = Xw * 760 mmHg

Xw = 745/760 = 0.98

Molar fraction of the solute = 1 - 0.98 = 0.02

Answer: 0.02