At a pressure of 760 torr, formic acid (HCO₂H; boiling point = 100.7 °C) and water (H₂O; boiling point = 100.0 °C) form an azeotropic mixture, boiling at 107.1 °C, that is 77.5% by mass formic acid. At the boiling point of the azeotrope (107.1 °C), the vapor pressure of pure formic acid is 917 torr and that of pure water is 974 torr.

(a) Calculate the vapor pressure of each component and the total vapor pressure at 107.1 °C if the solution had obeyed Raoult’s law for both components.

(b) Compare your answer to part a with the actual vapor pressure of the azeotrope. Is the deviation of this azeotropic mixture from Raoult’s law positive or negative?

(c) Compare the attractive forces between formic acid and water with those in the two pure substances.