Mod 5 Topic 4

Question 1

Explain the structure of ionic solids

Answer 1

Crystalline structure with alternating positive and negative ions attracted through electrostatic attraction.

Question 2

How strong are ionic bonds

Answer 2

The electrostatic attraction between ions (ionic bond) is a generally strong bond.

Question 3

How does water act as a solvent (bonding)

Answer 3

Water dissolves substances through either hydrogen bonding (with molecules) or ion-dipole bonding (with ionic substances).

Question 4

How does Ion dipole bonds work w/ water as a solvent

Answer 4

Forms between an ion (either positive or negative) and the dipole ends of water molecules.

cations form bonds with the negative oxygen.
anions forms bonds with the positive hydrogen.

Question 5

How strong are ion dipole bonds

Answer 5

Very strong

Question 6

Water w/ crystallisation

Answer 6

Water molecules become attracted to the ions of a salt and form a crystalline substance that exists in a set ratio of ions to water molecules.

Question 7

What happens to hydrated substances when heated

Answer 7

When hydrated substances are heated, the water will evaporate leaving behind an anhydrous substance.

Question 8

What are the two main energy changes when dissolving in water

Answer 8

An input of energy required to separate the ions in the ionic solid

Energy released when the ion dipole bonds form.

Question 9

What is the solubility of a solute

Answer 9

The maximum mass (g) of solute that can dissolve in 100 g of solvent at a given temperature. units in g/100g

Question 10

What is an unsaturated solution

Answer 10

A solution in which the maximum solute has not been dissolved.

Question 11

What is a saturated solution

Answer 11

A solution in which the maximum solute has been dissolved.

Question 12

What is a supersaturated solution

Answer 12

A solution in which more than the maximum solute has been dissolved.

Question 13

Does temp affect solute in a solution

Answer 13

Yes - The amount of solute in a solution is affected by the temperature of the solution.

Question 14

Define soluble, sparingly soluble, and insoluble in terms of g/100ml

Answer 14

Soluble - dissolves >1 g/100 mL
Sparingly soluble – dissolves between 0.1-1 g/100 mL
Insoluble – dissolves <0.1 g/100 mL

Question 15

How does heating or cooling the solution affect solute am.

Answer 15

If the solution is heated, the extra solute will dissolve.

If this solution is cooled, the solute will precipitate out. The temperature at which this happens is the temperature at which the solution is saturated.

Question 16

Why is a supersaturated solution unstable

Answer 16

it contains more dissolved solute than the solvent can normally hold at that temperature. If a crystal of solute is added, or the solution is bumped, the extra solute will crystallize out instantly.

Question 17

How do precipitates form bw two ionic solutions

Answer 17

When two ionic solutions are added, there will be four types of ions present (two cations, two anions).

In some situations one cation and one anion will combine to form a precipitate.

The other ions that dont participate are called spectator ions

Question 18

Solubility rules for Group 1, NH4 + and NO3 - (generally don’t reach saturation point)

Answer 18

All soluble, no exceptions

Question 19

Solubility rules for Cl-, Br-, I-, CH3COO- (generally don’t reach saturation point)

Answer 19

Soluble except for Pb2+, Ag+, Hg2+

Question 20

Solubility rules for SO4 2- (generally don’t reach saturation point)

Answer 20

Soluble except for Ag +, Pb 2+, Ca 2+, Sp 2+, Ba 2+, Hg2+

Question 21

Is an ionic compound ever totally insoluble

Answer 21

Technically, no ionic compound is completely insoluble in water, hence precipitation reactions are dynamic equilibrium systems.

Question 22

How does precipitate reactions work when in equilibrium

Answer 22

The ionic solid has ions pulled away to dissolve at the same rate at which ions are combining to form a solid ionic precipitate. RR(dissolve) = RR(formation)

Question 23

What does the size of Ksp indicate

Answer 23

Solubility -

Small Ksp = poorly soluble substance that produces few ions.

Large Ksp = highly soluble substance that produces many ions.

Question 24

What is molar solubility?

Answer 24

The concentration of ions in mol L⁻¹ in a saturated solution.

Question 25

How to determine Ksp using molar solubility

Answer 25

1) Write a balanced equation for the equilibrium 2) Convert solubility data into mol L-1 3) Determine the concentration for each of the ions 4) Write the equilibrium expression 5) Substitute data into the equilibrium expression to calculate Ksp

Question 26

When is the term solubility product used?

Answer 26

Only when the system is at equilibrium.

Question 27

What is the ionic product?

Answer 27

The equivalent of Q for ionic equilibria when the system is not necessarily at equilibrium.

Question 28

Difference between Q (ionic product) and Ksp (solubility product)

Answer 28

The Ionic Product (Q) is the product of ion concentrations in a solution at any moment (showing the actual state) while Solubility Product (Ksp) is the ion product at saturation/equilibrium, indicating maximum solubility.

Question 29

What is the common ion effect?

Answer 29

Adding a common ion to a saturated solution decreases the solubility of the salt. When two ionic solutions are added they can have different ions (sodium sulfate and calcium nitrate) or they can have a common ion (sodium sulfate and calcium sulfate), If a solution of sodium sulfate is added to a solution of calcium sulfate, the addition of the extra sulfate ions will affect the equilibrium of the original calcium sulfate: CaSO4 (s) <=> Ca 2+(aq) + SO4 2- (aq)

Question 30

How does adding sulfate ions to a saturated calcium sulfate solution affect solubility?

Answer 30

The extra sulfate ions will drive the reaction to the left, making more solid calcium sulfate – thus the sparingly soluble calcium sulfate becomes even less soluble.