# Worksheet: Raoult's Law

Q1:

Consider a solution made by dissolving 342 g of sucrose in 127 mL of water at . The vapor pressure of water at is 0.095 atm and the density of water at is 0.992 g/mL. What is the vapor pressure of the sucrose/water solution? The molar mass of sucrose is 180.2 g/mol.

Q2:

The vapor pressure of pure liquid toluene at 300 K is , and the vapor pressure of pure liquid benzene at 300 K is . The mole fraction of toluene in a toluene-benzene mixture is 0.6000 and the temperature is 300 K. Assuming that mixtures of toluene and benzene behave as ideal solutions, calculate the total vapor pressure of the mixture and the mole fraction of toluene in the vapor .

• A ; (in vapor)
• B ; (in vapor)
• CThere is not enough information provided to answer this question.
• D ; (in vapor)

Q3:

Consider a toluene-benzene solution in which the mole fraction of toluene is 0.3300. At a temperature of 300 K, the total vapor pressure of this solution is 7.89 kPa, and the partial pressures of the toluene and benzene constituents of the vapor are and , respectively. At 300 K, the vapor pressure of pure liquid toluene is and the vapor pressure of pure liquid benzene is . What are the activities and activity coefficients of toluene and benzene in this solution?

• A ; ; ;
• B ; ; ;
• CThere is not enough information provided to answer this question.
• D ; ; ;

Q4:

Consider a 0.01 M aqueous solution of . How will the vapor pressure of this solution compare with the vapor pressure of pure liquid water?

• AIt will be the same.
• BIt will be higher.
• CThere is not enough information provided to answer this question.
• DIt will be lower.

Q5:

The vapor pressure of methanol is 94 torr at . The vapor pressure of ethanol is 44 torr at the same temperature. A mixture consists of 50.0 g of methanol and 50.0 g of ethanol, both of which behave ideally.

What is the mole fraction of methanol in the solution?

What is the vapor pressure of methanol above the solution at ?

What is the mole fraction of methanol in the vapor above the solution?

Q6:

Consider a dilute liquid solution comprised of solvent and solute . For this system, which of the following statements is incorrect?

• AAdditions of more solute to the solution will always lower the chemical potential of the solvent.
• BThe chemical potential of in solution is always less than the chemical potential of pure liquid (at fixed values of pressure and temperature).
• CAdditions of a nonvolatile solute to the solution will always lower the vapor pressure of the solution.
• DAt any given temperature, the vapor pressure of the solution will always be less than the vapor pressure of the pure solvent.