Chemical change

Question 1

Explain what is meant by oxidation and

reduction (2 meanings)

Answer 1

Oxidation is gain of oxygen
Reduction is loss of oxygen
OIL RIG Oxidation is loss of electrons
Reduction is gain of electrons

Question 2

Reactivity series of metals

Answer 2

Potassium
Sodium
Lithium
Calcium
Magnesium
Zinc
Iron
Copper

Question 3

What makes one metal more reactive than

another?

Answer 3

It has a greater tendency to form positive ions

Question 4

What is a displacement reaction and give an

example?

Answer 4

More reactive metal replaces less reactive metal in
compound
Magnesium + iron nitrate  magnesium nitrate + iron

Question 5

How can metals be extracted from their

oxides?

Answer 5

Unreactive metals e.g. gold found as the metal itself
If below carbon in reactivity series – use carbon to displace
them from the oxide
If above carbon – use electrolysis

Question 6

What do acids and alkalis always contain?

Answer 6

Acids – H + ions

Alkalis – OH - ions

Question 7

State the ways you can make soluble salts

by writing the general equations

Answer 7

Acid + metal  salt + hydrogen
Acid + alkali  salt + water
Acid + metal oxide  salt + water
Acid + carbonate  salt + water + carbon dioxide

Question 8

What type of salt does each acid make?

Answer 8

Hydrochloric acid (HCl) - chloride
Sulfuric acid (H 2 SO 4 ) - sulfate
Nitric acid (HNO 3 ) - nitrate

Question 9

Explain why a metal reacting with an acid is

a redox reaction.

Answer 9

The metal is oxidised (loses electrons) to form a positive ions
The hydrogen ion is reduced (gains electrons) to a hydrogen
atom

Question 10

Be able to write word equations

Ionic equations

Half equations

Answer 10

Magnesium + hydrochloric acid  magnesium chloride
+ hydrogen
Mg + 2H +  Mg 2+ + H 2

Mg – 2e -  Mg 2+
2H + + 2e -  H 2

Question 11

A base neutralises an acid. Give examples of a

soluble and insoluble base.

Answer 11

Soluble base (alkali) e.g. Sodium hydroxide
Insoluble base e.g. Zinc oxide

Question 12

What is the neutralisation equation?

Answer 12

H + + OH -  H 2 O

Question 13

Define a strong and weak acid and give examples of

both.

Answer 13

Strong acid – fully ionised in solution e.g. nitric acid

Weak acid – partially ionised in solution e.g. ethanoic acid

Question 14

Describe the pH scale

Answer 14

pH 1 – Red – Strong acid
pH 6 – Yellow – Weak acid
pH 7 – green – neutral
pH 8 – blue - weak alkali
pH 14 – purple – strong alkali

Question 15

As the pH concentration decreases by one unit……..

Answer 15

The hydrogen ion concentration increases by a factor of 10

Question 16

Describe how to make copper sulfate crystals using

an insoluble base and an acid.

Answer 16

• Warm the acid
• Add copper oxide to excess
• Filter the mixture
• Warm the copper sulfate solution over a water
bath til crystals first appear
• Pour into a petri dish and leave to crystallise

Question 17

Write definitions for the following:

Answer 17

Electrolysis – Using electricity to separate compounds
Cathode – Negative electrode
Anode – Positive electrode
Electrolyte - Compound is being separated into elements

Question 18

In electrolysis, what always happens to the

(movement and electrons):

Answer 18

Metal ions – Move to the negative electrode and gains
electrons
Non-metal ions – Move to the positive electrode and lose
electrons

Question 19

Describe the process of extracting aluminium from
aluminium oxide using electrolysis (think about the
electrodes, electrolyte, half equations)

Answer 19

• Dissolve aluminium oxide into cryolite
• Al 3+ + 3e -  Al
• 2O 2- - 4e -  O 2
• Carbon electrodes wear away as the oxygen
reacts with them to form carbon dioxide

Question 20

What are the rules for the electrolysis of aqueous

compounds?

Answer 20

• At the negative electrode – least reactive out of
metal or hydrogen
• At the positive electrode – group 7 given out if
not oxygen from hydroxide.