Solubility and salt preparation

Question 1

2. What is a solvent?

Answer 1

A liquid that a solute dissolves in

Question 1

1. What is a solute?

Answer 1

A solid that dissolves in a solvent

Question 2

3. What is a solution?

Answer 2

The mixture produced when a solute is dissolved in a solvent

Question 3

4. What is a saturated solution?

Answer 3

The maximum mass of solute that can dissolve in a solvent for a given temperature

Question 4

5. How does solubility increase with temperature?

Answer 4

Solubility increases with temperature, the higher the temperature, the more solute can be dissolved

Question 5

How is solubility measured?

Answer 5

In [mass] (g)/100g [liquid solute is dissolving in]

Question 6

Solubility rules

Answer 6

Halides (iodides, chlorides, bromides) Soluble except lead (Pb) and silver (Ag) halides
Hydroxides and oxides (OH) Insoluble except group 1 and ammonium
Sulfates (SO4) Soluble except barium (Ba) and calcium (Ca)
Group 1 and ammonium (NH4) Always soluble
Carbonates (CO3) Insoluble except group 1 and ammonium (calcium carbonate is slightly soluble in water)
Nitrates Always soluble

Question 7

Formulae of sulphate ions

Answer 7

SO4 2-

Question 8

Formulae of nitrate ions

Answer 8

NO3 -

Question 9

Formulae of carbonate ions

Answer 9

CO3 2-

Question 10

Formulae of hydroxide ions

Answer 10

OH-

Question 11

Formulae of sulphuric acid

Answer 11

H2SO4

Question 12

Formulae of nitric acid

Answer 12

HNO3

Question 13

Formulae of Hydrochloric acid

Answer 13

HCL

Question 14

Formulae of ammonia

Answer 14

NH3

Question 15

Formulae of ammonium

Answer 15

NH4+

Question 16

Formulae of lead ion

Answer 16

Pb 2+

Question 17

Formulae of hydrogen ion

Answer 17

H +

Question 18

Formulae of silver ion

Answer 18

Ag +

Question 19

Formulae of zinc ion

Answer 19

Zn 2+

Question 20

What is an acid?

Answer 20

A donor of H+ ions (HCl, HNO3, H2SO4)(CH3COOH – ethanoic acid)

Question 21

What is a base?

Answer 21

A source of OH- ions that reacts with an acid

Question 22

What is a salt made up of?

Answer 22

A metal bromide/nitrate/sulfate/iodide/chloride

Question 23

What happens when two salt solutions are mixed together that produce soluble salts ?

Answer 23

There is no reaction as the products of the reaction are both soluble, so ions diffuse around the solution

Question 24

What is a precipitate?

Answer 24

An insoluble solid that is produced in a precipitation reaction

Question 25

How are precipitates formed?

Answer 25

By precipitation reactions Two soluble salts react to make an insoluble salt and a soluble salt

Question 26

What can and cannot be made using a precipitation reaction?

Answer 26

Soluble salts cannot be made using the precipitation reaction They would be made using the copper(II)sulfate method that starts from an acid and an alkali Example: copper(II)oxide + sulfuric acid —> copper(II)sulfate + water Insoluble salts can be made using the precipitation reaction Soluble salt + soluble salt —> insoluble salt + soluble salt

Question 27

How is a pure, dry sample of an insoluble salt prepared?

Answer 27

- Mix solution of two soluble reactants - Filter mixture (insoluble salt will remain on filter paper) - Wash the salt with distilled water (makes sure the sample is pure) - Leave the salt to dry

Question 28

Rules when writing ionic equations

Answer 28

Write out a balanced symbol equation Ionic compounds (soluble), acids and bases dissociate (split up) Cancel out terms that appear on both sides of the equation (spectator ions) Substances that do not dissociate do not become charged (eg H2)

Question 29

What types of compounds are usually coloured?

Answer 29

Transition metal compounds

Question 30

Copper(II)sulfate colour

Answer 30

Light blue solution

Question 31

Lead(II)nitrate colour

Answer 31

Colourless solution

Question 32

Iron(III)chloride colour

Answer 32

Yellow solution

Question 33

Table recording results of precipitation reactions practical with colour changes

Answer 33

Copper(II)sulfate + potassium iodide Light blue solution to red-brown precipitate Copper(II)sulfate + sodium hydroxide Bright blue precipitate (gelatinous appearance) formed in light blue solution Copper(II)sulfate + potassium sulfate No change - stayed a light blue solution Lead(II)nitrate + potassium iodide Colourless to opaque bright yellow precipitate Lead(II)nitrate + sodium hydroxide White preciptate formed from colourless solution Lead(II)nitrate + potassium sulfate No colour change – stayed a colourless solution Iron(III)chloride + potassium iodide No colour change – stayed a yellow solution Iron(III)chloride + sodium hydroxide Iron(III)chloride + potassium sulfate No colour change – stayed a yellow solution