Which solution has the highest vapor pressure?
A) 0.75 mol of a nonvolatile compound in 750 g of ethanol
B) 0.75 mol of a volatile compound in 750 g of ethanol
C) 1.5 mol of a nonvolatile compound in 750 g of ethanol
D) Solutions A and B have the same vapor pressure and it is higher than the vapor pressure of solution C.
E) Not enough information is given to determine which solution has the highest vapor pressure.

Question

Quizplus · Accepted Answer

According to Raoult's law, the vapor pressure of a solution is directly proportional to the mole fraction of the volatile solute in the solution. Therefore, a solution with a higher mole fraction of a volatile solute will have a higher vapor pressure. Choice B has 0.75 mol of a volatile compound in 750 g of ethanol, which is the highest mole fraction of a volatile solute among the given choices. Therefore, choice B will have the highest vapor pressure.

Which Solution Has the Highest Vapor Pressure