Chapter 3: 3.2 Solubility of Ionic Compounds

Question 1

Define:

Solubility of a substance

Answer 1

The amount of that substance that will dissolve in a certain volume of a specific solvent, and is usually expressed in grams per litre or in moles per litre

Question 2

Define:

1. Soluble compound
2. Slightly soluble compound
3. Insoluble compound

Answer 2

1. 10 g or more can dissolve in 1 L of solvent
2. 0.1-10 g can dissolve in 1 L of solvent
3. Less than 0.1 g can dissolve in 1 L of solvent

Question 3

Define:

1. Solvent
2. Solute

Answer 3

1. A liquid or a gas that dissolves another solid, liquid, or gas
2. The substances that dissolve in a solvent forming the resultant solution

Question 4

Define:

Saturated solution

Answer 4

When the solution reaches a point where an equilibrium is established between the undissolved solid and the free ions (no more solid will dissolve in the solution)

Question 5

What is K sp?

Answer 5

An equilibrium constant called the solubility product or the solubility product constant

Question 6

True or False:

Salts that are very soluble have a small K sp value

Answer 6

False, salts that are very soluble have a very large K sp value

Question 7

State:

The dissolution of an ionic solid of composition AxBy

Answer 7

AxBy (s) ⇌ xA^a+ (aq) + yB^b- (aq)

Question 8

State:

K sp expression for a heterogenous equilibrium

Answer 8

K sp = [A^a+]^x[B^b-]^y

Question 9

How will the solubility product constant vary?

Answer 9

As it is an equilibrium constant:
1. It will only vary with temperature
2. At a given temperature, it will vary depending on conditions (presence of ions in solution etc.)

Question 10

SHow the difference between:

Saturated and Unsaturated Solutions

Answer 10

• Unsaturated: The quantity of a species in solution is less than that required for equilibrium with the solid
• Saturated: Equilibrium between solid and species in solution

Question 11

In terms of K sp:

What is the reaction quotient (Q) known as?

Answer 11

Ion product

Question 12

If the concentrations of ions in solution are given, what can the K sp value and the Q value be used to determine?

Answer 12

Can be compared to determine whether a solid (precipitate) will be present:
1. Q < K sp: No solid present (unsaturated)
2. Q = K sp: System in equilibrium (saturated)
3. Q > K sp: Solid present (supersaturated)

Question 13

Describe:

The common ion effect

Answer 13

The solution may already contain an ion in common with the dissolving salt, thus the common ion effect can significantly reduce the solubiity of the solid relative to that in pure water

Question 14

How can the solubility and common ion effect be observed?

Answer 14

Using ICE Table (Initial, Change, Equilibrium)

Question 15

What is the difference between solubility and solubility product constant?

Answer 15

1. Solubility: The amount of a given substance that dissolves in a given volume of solvent at a given temperature, and may be expressed in g/L or mol/L
2. Solubility product constant: An equilibrium constant (K sp)