18. an equal number of moles of nacl and mgf2 are dissolved in equal volumes of water. which solution has the higher (6 points) a. boiling point b. vapor pressure c. freezing point + 2 extra points if you can explain why.

a. Boiling point: MgF₂ will have the higher boiling point.

b. Vapor pressure: NaCl will have the higher vapor pressure.

c. Freezing point: NaCl will have the higher freezing point.

Explanation:

This is the change in the collegative properties of water by adding a solute particles.The addition of solute to water cause elevation of boiling water and depression of vapor pressure and freezing point.The no. of ions of the dissolved solute in the solution have a great effect on the collegative properties of water, what is known as van 't Hoff factor. The van 't Hoff factor is the ratio between the actual concentration of particles produced when the substance is dissolved and the concentration of a substance as calculated from its mass. For most ionic compounds dissolved in water, the van 't Hoff factor is equal to the number of discrete ions in a formula unit of the substance. This is true for ideal solutions only, as occasionally ion pairing occurs in solution.

MgF₂ will be ionized into 3 ions (1 of Mg²⁺, 2 of F⁻) while NaCl will be ionized into 2 ions (1 of Na⁺, 1 of Cl⁻).

So, MF₂ will cause elevation of boiling point, depression in vapor pressure, and depression of freezing point higher than the effect of NaCl.

Thus:

a. Boiling point: MgF₂ will have the higher boiling point.

b. Vapor pressure: NaCl will have the higher vapor pressure.

c. Freezing point: NaCl will have the higher freezing point.