3.6

Question 1

Saturated solution

Answer 1

Contains the maximum amount of a solute that will dissolve in a given solvent at a given temperature

Question 2

Unsaturated solution

Answer 2

Contains less solute than it has the capacity to dissolve

Question 3

Supersaturated solution

Answer 3

Contains more solute than is present in a saturated solution - not very stable

Question 4

Crystallization

Answer 4

The process in which dissolved solute comes out of a supersaturated solution and forms crystals

Question 5

The ease with which a solute particles replaces a solvent molecule depends on the relative strength of three types of interactions

Answer 5

(1) Solvent-solvent
(2) Solute-solute
(3) Solvent-solute

Question 6

Three steps of the solution process

Answer 6

(1) Separation of solvent molecules
(2) Separation of solute molecules
(3) Solvent and solute molecules mix

Question 7

The solution process is favorable, or exothermic if

Answer 7

The solute-solvent attraction is stronger than the solvent-solvent attraction and solute-solute attraction

Question 8

The solution process is endothermic if

Answer 8

The solute-solvent interaction is weaker than the solvent-solvent and solute-solute interactions

Question 9

Two liquids are miscible if

Answer 9

they are completely soluble in each other in all proportions

Question 10

Solvation

Answer 10

The process in which an ion or a molecule is surrounded by solvent molecules arranged in a specific manner
–> Hydration when solvent is water

Question 11

Percent by mass

Answer 11

= mass of solute / mass of soln * 100%

Question 12

Mole fraction of component A

Answer 12

= moles of A / sum of moles of all comp

Question 13

Molarity

Answer 13

= moles of solute / liters of soln

Question 14

Molality

Answer 14

= moles of solute / mass of solvent (kg)

Question 15

Fractional crystallization

Answer 15

The separation of a mixture of substances into pure components on the basis of their differing solubilities

Question 16

When does fractional crystallization work best?

Answer 16

The compound to be purified has a steep solubility curve, or else much will remain dissolved as the solution is cooled

Question 17

Henry’s law

Answer 17

The solubility of a gas in a liquid is proportional to the pressure of the gas over the solution

Question 18

Henry’s law formula

Answer 18

c = kP
- c is molar concentration (mol/L)
- P is pressure of the gas over the solution at equilibrium. With multiple glasses, P is partial pressure
- k is a constant dependent only on temp

Question 19

Colligative properties

Answer 19

Properties that depend only on the number of solute particles in solution and not on the nature of the solute particles

Question 20

Four colligative properties

Answer 20

(1) vapor-pressure lowering
(2) boiling-point elevation
(3) freezing-point depression
(4) osmotic pressure

Question 21

Raoult’s law

Answer 21

Vapor pressure of a solvent over a solution, P1, is given by the vapor pressure of the pure solvent, P1° times the mole fraction of the solvent in the solution, X1

Question 22

Why is the vapor pressure of a solution less than that of a pure solvent?

Answer 22

• A solution is more disordered than a pure solvent
• Difference in disorder between a solution and a vapor is less than that between a pure solvent and a vapor
• Solvent molecules have less of a tendency to leave a solution than to leave a pure solvent to become vapor

Question 23

If both components of a solution are volatile, what is its vapor pressure?

Answer 23

P = P1 + P2 = X1P1° + X2P2°

Question 24

Volatile

Answer 24

Measurable vapor pressure

Question 25

Ideal solution

Answer 25

Any solution that obeys Raoult’s law

Question 26

Case I of non ideal solution

Answer 26

IMF between A and B are weaker than between A and B molecules, greater tendency for these molecules to leave the solution than in the case of an ideal solution.
VP greater than expected, resulting in a positive deviation.
Heat of solution is positive (mixing is endothermic)

Question 27

Case II of non ideal solution

Answer 27

IMF between A and B are greater than between A and B molecules, less tendency for these molecules to leave the solution than in the case of an ideal solution.
VP less than expected, resulting in a neg deviation.
Heat of solution is negative (mixing is exothermic)

Question 28

Fractional distillation

Answer 28

Procedure for separating liquid components of a solution based on their different boiling points

Question 29

Boiling point elevation (∆Tb)

Answer 29

Boiling point of the solution (Tb) minus the boiling point of the pure solvent (Tb°)
∆Tb = Tb - Tb°
∆Tb = Kb(m)
- Kb is molal boiling-point elevation constant and m is molality (B/c it is ind of T)

Question 30

Freezing point depression (∆Tf)

Answer 30

The freezing point of the pure solvent (Tf°) minus the freezing point of the solution (Tf)

Question 31

Why is ∆Tf a positive quantity

Answer 31

• Transition from the disordered to ordered state
• A solution has greater disorder than the solvent, so more energy must be removed to create order than for a pure solvent
• A solution has a lower freezing point than its solvent

Question 32

When will a solution boil?

Answer 32

Boiling point is the temperature at which vapor pressure equals external atmospheric pressure

Question 33

Semipermeable membrane

Answer 33

Allows the passage of solvent molecules but blocks the passage of solute molecules

Question 34

Osmotic pressure (π)

Answer 34

Pressure required to stop osmosis

Question 35

What causes water to move from the pure solvent into the solution during osmosis?

Answer 35

Vapor pressure of pure water is higher than the vapor pressure of the solution, so there is a net transfer of water into the solution

Question 36

Formula for osmotic pressure

Answer 36

π = MRT (molarity * gas constant * absolute temperature)