Solution Equilibria

Question 1

In diagrams you must always..

Answer 1

Label (otherwise no marks) and correct molar ratio

Question 2

What is the forces/bonding in the dissolution of ionic compounds?

Answer 2

Intermolecular forces

Question 3

Describe what will happen to the solute about intermolecular forces.

Answer 3

A solute will dissolve if the formation of intermolecular forces between the solute and solvent are more favourable than the existing intermolecular forces between solute molecules and solvent molecules.

Question 4

Why are ionic compounds able to be dissolved?

Answer 4

Ionic compounds (or salts) are able to dissolve in water because they undergo the process of disassociation and then the individual ions form ion-dipole forces with water.

Question 5

Will the solute-solute interactions break or form?

Answer 5

Break - input of energy is required

Question 6

Solvent-solvent interactions are

Answer 6

Dipole-dipole, hydrogen-bonding and dispersion forces.

Question 7

Solute-solvent interactions will be formed…

Answer 7

ion-dipole forces between the ions and water

Question 8

The enthalpy of dissolution of an ionic substance in water is dependent on

Answer 8

The balance of these energy inputs and outputs, and thus will change for each substance

Question 9

During the dissolution, the entropy ___

Answer 9

of the system increases (more disorder as the ions break from the lattice)

Question 10

Is dissolution an equilibrium?

Answer 10

Yes

Question 11

What is an unsaturated solution?

Answer 11

A small amount is dissolved (but not enough to make a saturated solution.
Static equilibrium is established since dissolution heavily favours the solute.

Question 12

State the solubility product equation:

Answer 12

AB (s) <—> A+ (aq) + B-(aq)
Keq = [A+][B-]

Question 13

Saturated solution is when….

i) Solute dissolved
ii) DE
iii) Diassociation = rate

Answer 13

sufficient solute is dissolved such that a dynamic equilibrium is established. Rates of the forward and backward reactions become equal gradually.
Dissassociation is occurring at the same rate as precipitation and hence the ions are in constant motion

Question 14

Supersaturated

Answer 14

Formed when a solution is heated or cooled to allow for more solute to be dissolved
- Will come to dynamic equilibrium
- crystallisation occurs

Question 15

How to calculate the Ksp value?
(procedure)

Answer 15

1. Write a balanced chemical equation
2. Draw an ICE table and insert the provided data
3. Write an expression for the Ksp value
4. Unless provided, use the given data sheet to find it
5. Determine the molar solubility of the substance by using all the information.

Question 16

What is molar Solubility?

Answer 16

Molar solubility is the solubility of a substance expressed as the amount of solute (in moles) dissolved per one liter of solution.

Question 17

What is the ionic product? (Qsp)

Answer 17

The quotient of the ionic diassociation

Question 18

If Qsp<Ksp, the solution is _____

Answer 18

Unsaturated. More of the ionic solid will dissolve if added
lies to the right - not yet reached completion

Question 19

If Qsp = Ksp, the solution is ____

Answer 19

Saturated anda at equilibrium

Question 20

Qsp >Ksp, the solution is ______

Answer 20

Supersaturated, and ionic solid will precipitate
(goes to over-completion)
Lies to the left

Question 21

The common ion effect states that

Answer 21

the solubility of salts dissolved in such solutions will greatly decrease compared to dissolution in pure water

Question 22

What is the principle behind common ion effect?

Answer 22

Le Chatelier’s principle - As the increased concentration of an ion will cause the equilibrium to favour the reverse reaction (i.e. precipitation)

Question 23

What happens if an insoluble or sparingly soluble salt is added to a solution with a common ion?

Answer 23

The conc. of the common ion will not change much and will be close to its original conc.