Question

Match the vapor pressure diagrams with the solute–solvent combinations and explain your answers.

a.

b.

c

d.

Short answer

The given combinations of solute-solvent will show the following vapor pressure graph:

Solute-solvent combination	Vapor pressure diagram
Acetone and water	Negative deviation (b diagram)
Ethanol and water	Positive deviation (a diagram)
n-heptane and n-hexane	Ideal solution (c diagram)
n-heptane and water	Positive deviation (a diagram)

Step-by-step solution

Explanation regarding Subpart (a):

From the given graphs, the solution of acetone and water shows a negative deviation. Because the bond strength of acetone and water is stronger as compared to the bond between acetone-acetone and water-water. This is the reason that the vapor pressure of the pure solvents or solute is less than that of their solution.

Thus, when observed the value of vapor pressure of the solution, comes less than the vapor pressure of an ideal solution

Explanation regarding Subpart (b):

From the given graphs, the solution of ethanol and water shows a positive deviation. Because the bond strength of ethanol and water is weaker as compared to the bond between ethanol-ethanol and water-water. This is the reason that the vapor pressure of the pure solvents or solute is more than that of their solution.

Thus, when observed the value of vapor pressure of the solution, comes more than the vapor pressure of an ideal solution.

Explanation regarding Subpart (c)

From the given graphs, the solution of n-heptane and n-hexane shows ideal behavior as they follow Raoult’s law. The bond strength of ethanol-water, ethanol-ethanol, and water-water is almost similar or equal. This is the reason that whenever the bond if formed there is no loss or gain of heat.

Thus, when observed the value of vapor pressure of the solution, shows ideal behavior and gives a straight-line graph.

Explanation regarding Subpart (d)

From the given graphs, the solution of n-heptane and water shows a positive deviation. Because the bond strength of n-heptane and water is weaker as compared to the bond between heptane-heptane and water-water. This is the reason that the vapor pressure of the pure solvents or solute is more than that of their solution.

Thus, when observed the value of vapor pressure of the solution, comes more than the vapor pressure of an ideal solution.