16 Aqueous Solution

Question 1

Water as a solvent

Answer 1

Most molecular substances are insoluble in water but a good solvent for some polar molecular compounds.

2 main reasons it’s a good solvent:
By forming hydrogen bonds with water
By ionising to form hydrated ions.

Question 2

How does ethanol dissolve in water?

Answer 2

Water molecules break
Ethanol molecules break
Ethanol molecules and water molecules form an aqueous solution

Question 3

Examples of soluble compounds in water

Answer 3

Ammonia, sucrose (sugar) fructose glucose.
The more polar they are, the more likely it is to dissolve.

Question 4

Molecules that ionise in water

Answer 4

Highly polar molecular compounds form ions when dissolved.
Eg HCL when added to water, the hydrogen atom has a strong attraction to oxygen causing the covalent bond to break.
Ions form CL H3O+ become hydrated, held together ion-dipole attractions

Question 5

What chemicals ionise in water

Answer 5

Nitric acid sulphuric acid and ethanoic acid dissolve in water by ionising. Ammonia ionises to form ammonium

Answer 6

The polar water molecules r attracted positive and negative ions of ionic solute. Ion dipole dipole forces hold molecules to the ions. These ions with water molecules attracted to them are called complex ions.

Answer 7

Electrostatic attraction attracts negative ions of NACL in a lattice and the hydrogen atoms in polar water molecules.
Electrostatic attraction also occurs between positive ions in lattice and the oxygen atoms in the water.

Question 8

Why dont Insoluble ions dissolve in water

Answer 8

because energy required to seperate ions from lattice is greater than the energy released when ions r hydrated.

Question 9

What are soluble salts

Answer 9

SNAPE

Sodium
Nitrate
Ammonium
Potassium
Ethanoate

Question 10

Supersaturated solution

Answer 10

Holds more solute than theoretically possible at that temperature.

Question 11

Saturated solution

Answer 11

Holds maximum amount of solute possible

Question 12

Unsaturated solution

Answer 12

Could hold more solute

Question 13

Precipitation reactions are good for:

Answer 13

To remove minerals from drinking water and

Question 14

Spectator ions are

Answer 14

Ions that remain uncharged in a solution when 2 ionic compounds are mixed and a precipitate form

Question 15

How do precipitates get their colour

Answer 15

Determined by the colour of their ions. Colourless ions form white precipitate.

Question 16

How do u describe observations on precipitation

Answer 16

• colour of reactants and products
• give reasoning why

Question 17

Ionic equations

Answer 17

Includes only atoms which undergo a chemical change during reactions and therefore are usually written as ions. Do not include spectator ions

Question 18

Full equation

Answer 18

• balanced
• states of matter
• all chemicals are included

Question 19

Molarity

Answer 19

Moles/litre