Chemical changes

Question 1

What type of separation process would you use to separate a soluble salt?

Answer 1

Crystallisation

Question 2

When there are several ions in solution, which ion will collect at the anode?

Answer 2

At the cathode: Hydrogen is produced if the metal is more reactive than Hydrogen

Question 3

Write the formulae of Magnesium Chloride

Answer 3

MgCl₂

Question 4

Higher What is a ‘weak’ acid?

Answer 4

An acid that is only partially ionised in water.

Question 5

Describe how you would make a pure, dry sample of a soluble salt using an insoluble base and an acid.

Answer 5

• Add base in excess to acid.
• Filter excess base.
• Crystallisation – to separate salt from its solution.

Question 6

What is the name for the reaction when an acid reacts with an alkali to make a salt + water?

Answer 6

Neutralisation reaction

Question 7

Higher Explain why the reaction below is a redox reaction. Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g)

Answer 7

• Zinc atoms are oxidised. • Hydrogen atoms are reduced. • Hence reduction and oxidation happen at the same time so it’s called a redox reaction.

Question 8

Higher Fill in the blanks: Oxidation is the _____ of electrons. Reduction is the _____ of electrons.

Answer 8

• Oxidation is the loss of electrons • Reduction is the gain of electrons

Question 9

Complete the general equation

Acid + Metal Carbonate →

Answer 9

Acid + Metal carbonate → Salt + Water + carbon dioxide

Question 10

Why is cryolite used in the electrolysis of aluminium oxide?

Answer 10

To lower the melting point of aluminium oxide (to save energy and costs)

Question 11

Higher In the following equation, state which species are oxidised and which are reduced? 2Fe2O3 + 3C → 4Fe + 3CO2

Answer 11

• 2Fe2O3 (Iron oxide) is reduced • 3C (carbon) is oxidised

Question 12

Name the ‘salt’ produced when the following chemicals react

Magnesium oxide + sulfuric acid

Answer 12

Magnesium sulfate

Question 13

If an atom is very reactive, is it more or less likely to turn into an ion?

Answer 13

More likely

Question 14

What is that name for the reaction that involves the removal of oxygen?

Answer 14

Reduction

Question 15

Write an ionic equation for neutralisation

Answer 15

H+ (aq) + OH- (aq) → H2O (l)

Question 16

In electrolysis, what is the negative electrode called?

Answer 16

Cathode

Question 17

Why is gold found naturally in the Earth, but other metals are locked up in compounds?

Answer 17

Gold is unreactive

Question 18

In the electrolysis of lead bromide, what collects at The negative electrode (the cathode)

Answer 18

Lead (at the cathode)

Question 19

Name the ion found in acidic solutions

Answer 19

Hydrogen ion, H+

Question 20

Write the formulae of the following salts using the formulae of ions provided below. Sodium Chloride

Answer 20

NaCl

Question 21

Higher During electrolysis, what happens to ions at the Anode?

Answer 21

At the Anode: Ions lose electrons and turn into atoms (Oxidation)

Question 22

Complete the general equation

Metal + Acid →

Answer 22

Metal + Acid → Salt + Hydrogen

Question 23

In the electrolysis of lead bromide, what collects at The positive electrode (the anode)

Answer 23

Bromine (at the anode)

Question 24

Higher During electrolysis, what happens to ions at the Cathode?

Answer 24

At the Cathode: Ions gain electrons and turn into atoms (Reduction)

Question 25

What is the name of the liquid that is electrolysed.

Answer 25

Electrolyte

Question 26

Higher If you compared the pH of a 1M Strong Acid and a 1M Weak acid, which would have the higher pH and why?

Answer 26

The weaker acid will have the higher pH because it only partially ionises in water (or vice versa).

Question 27

What is the name for the reaction that involves the gaining of oxygen?

Answer 27

Oxidation

Question 28

Name the ‘salt’ produced when the following chemicals react Iron hydroxide + hydrochloric acid

Answer 28

Iron chloride

Question 29

Complete the general equation Metal + Water →

Answer 29

Metal + Water → Metal hydroxide + Hydrogen

Question 30

Higher In the following equation, state which species are oxidised and which are reduced? a) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)

Answer 30

• Magnesium atoms (Mg) are oxidised. • Hydrogen ions (H+) are reduced.

Question 31

When there are several ions in solution, which ion will collect at the cathode?

Answer 31

At the anode: Oxygen is produced unless the solution contains halide ions, then the halogen is produced.

Question 32

What type of separation process would you use to separate an insoluble salt?

Answer 32

Filtration

Question 33

In electrolysis, what is the positive electrode called?

Answer 33

Anode

Question 34

Higher Write half equations at the anode and cathode for the electrolysis of water.

Answer 34

• Anode: 4OH- - 4e- → O2 + 2H2O or 4OH- → O2 + 2H2O + 4e- • Cathode: 2H+ + 2e- → H2

Question 35

What type of reaction is shown by the equation below? magnesium + oxygen → magnesium oxide

Answer 35

Oxidation

Question 36

What is the pH of a neutral solution?

Answer 36

7

Question 37

Complete the general equation Acid + Metal oxide →

Answer 37

Acid + Metal oxide → Salt + Water

Question 38

To which electrode are negative ions attracted to?

Answer 38

Positive electrode (opposites attract)

Question 39

Name the ‘salt’ produced when the following chemicals react Sodium carbonate + nitric acid

Answer 39

Sodium nitrate

Question 40

Why can’t aluminium be extracted by reduction with carbon?

Answer 40

Aluminium is more reactive than carbon

Question 41

Higher Write the half equations at the anode and cathode for the electrolysis of lead bromide.

Answer 41

• Anode: 2Br- - 2e- → Br2 or 2Br- → Br2 + 2e- • Cathode: Pb2+ + 2e- → Pb

Question 42

Higher Write an ionic equation for each of the displacement reactions below: Fe + CuCl2 → Cu + FeCl2

Answer 42

Fe(s) + Cu2+ (aq) → Cu(s) + Fe2+ (aq)

Question 43

What is the pH range of acids?

Answer 43

0-6

Question 44

What chemical reaction is shown by the equation below to extract iron from iron oxide? Iron oxide + carbon → iron + carbon dioxide

Answer 44

Reduction (with carbon)

Question 45

What two non-metals are often included in the reactivity series?

Answer 45

Hydrogen and Carbon

Question 46

To which electrode are positive ions attracted to?

Answer 46

Negative electrode (opposites attract)

Question 47

What is the pH range of alkalis?

Answer 47

8-14

Question 48

Why does the positive electrode have to be regularly replaced in the extraction of aluminium oxide?

Answer 48

Because oxide ions react with the carbon electrode… • Releasing CO2… • Meaning the electrodes gradually degrade

Question 49

Why does a metal compound have to be molten or dissolved for electrolysis to work?

Answer 49

Because the ions need to be free to flow

Question 50

Why must aluminium be extracted by electrolysis?

Answer 50

It is more reactive than carbon (and therefore can’t be extracted by reduction with carbon)

Question 51

What is the name for the liquid that contains the ions in the electrolysis process?

Answer 51

Electrolyte

Question 52

Higher Write an ionic equation for each of the displacement reactions below: Mg + CuSO4 → Cu + MgSO4

Answer 52

Mg(s) + Cu2+ (aq)→ Cu(s) + Mg2+ (aq)

Question 53

Higher Give two examples of strong acids and two examples of weak acids.

Answer 53

• Strong acids include: Hydrochloric, Nitric and Sulfuric • Weak acids include: Carbonic, Ethanoic and Citric

Question 54

Put the following elements in order of reactivity from least to most reactive: iron / lithium / zinc / copper / potassium / calcium / sodium / magnesium

Answer 54

(least reactive) copper – iron – zinc – magnesium – calcium – lithium – sodium – potassium (most reactive)