Unit 1 - Oxidising & Reducing Agents

Question 1

What is oxidation?

Answer 1

Loss of electrons

Question 2

What is reduction?

Answer 2

Gain of electrons

Question 3

What is redox?

Answer 3

Reduction and Oxidation happening simultaneously

Question 4

What type of reaction is Cu(s) → Cu²⁺(aq) + 2e⁻?

Answer 4

Oxidation

Question 5

What type of reaction is 2Cl⁻(aq)→ Cl₂(g) + 2e⁻?

Answer 5

Reduction

Question 6

What type of reaction is MnO₄⁻(aq) + 8H⁺(aq) + 5e⁻ → Mn²⁺(aq) + H₂O?

Answer 6

Reduction

Question 7

What type of reaction is Fe²⁺(aq) → Fe³⁺(aq) + e⁻?

Answer 7

Reduction

Question 8

What is a spectator ion?

Answer 8

One which does not take part in the reaction. It is in the same state at the start and end of the reaction.

Question 9

Combine to form a redox reaction: 2I⁻(aq) → I₂(s) + 2e⁻ and Fe³⁺(aq) + e⁻ → Fe²⁺.

Answer 9

2I⁻(aq) + 2Fe³⁺(aq) → I₂(s) + 2Fe²⁺(aq)

Question 10

Name the reaction which happens in batteries and cells.

Answer 10

Redox

Question 11

What is an oxidising agent?

Answer 11

• An oxidising agent is a substance that accepts electrons.
• It causes other substances to be oxidised.
• It is reduced itself.

Question 12

What is a reducing agent?

Answer 12

• A reducing agent is a substance that donates electrons.
• It causes other substances to be reduced.
• It is oxidised itself.

Question 13

Identify the spectator ion(s) in the reaction Zn(s) + Cu²⁺(aq) + SO₄²⁻(aq) → Zn²⁺(aq) + SO₄²⁻(aq) + Cu(s).

Answer 13

• sulfate ions

SO₄²⁻(aq)

Question 14

Identify the oxidising agent in the reaction Zn(s) + Cu²⁺(aq) + SO₄²⁻(aq) → Zn²⁺(aq) + SO₄²⁻(aq) + Cu(s).

Answer 14

Copper ions

Cu²⁺(aq)

Question 15

Identify the reducing agent in the reaction Zn(s) + Cu²⁺(aq) + SO₄²⁻(aq) → Zn²⁺(aq) + SO₄²⁻(aq) + Cu(s).

Answer 15

Zinc

Zn(s)

Question 16

What type of substances tend to be reducing agents?

Answer 16

• Elements with low electronegativities tend to form ions by losing electrons and so act as reducing agents.
• In the periodic table, the strongest reducing agents are in group 1.
• In the electrochemical series, the strongest reducing agents are found at the top right.

Question 17

What type of substances tend to be oxidising agents?

Answer 17

• Elements with high electronegativities tend to form ions by gaining electrons and so act as oxidising agents.
• In the periodic table, the strongest oxidising agents are in group 7.
• In the electrochemical series, the strongest reducing agents are found at the bottom left.

Question 18

Is hydrogen peroxide an oxidising agent or a reducing agent?

Answer 18

Reducing agent

Question 19

Is the permanganate ion an oxidising agent or a reducing agent?

Answer 19

Oxidising agent

Question 20

Is the dichromate ion an oxidising agent or a reducing agent?

Answer 20

Oxidising agent

Question 21

Is carbon monoxide an oxidising agent or a reducing agent?

Answer 21

Reducing agent

Question 22

How is potassium permanganate commonly used as an oxidising agent?

Answer 22

Potassium permanganate can be used in fish tanks and ponds to kill parasites, bacteria and fungal infections in fish.
Potassium permanganate can be used as an oxidising agent for rocket fuel.

Question 23

How is sodium chlorate commonly used as an oxidising agent?

Answer 23

Sodium chlorate (Na⁺ClO₃⁻) is a powerful oxidiser used as a weedkiller and can be used to make explosives.

Question 24

How is chlorine commonly used as an oxidising agent?

Answer 24

• Chlorine is added to the water supply and to swimming pools to kill microorganisms.
• Bleach

Question 25

How are hypochlorite ions and hydrogen peroxide commonly used as oxidising agents?

Answer 25

• Bleach

Question 26

Where are oxidising agents found in the electrochemical series?

Answer 26

• The strongest oxidising agents are at the bottom of the left-hand column of the electrochemical series.

Question 27

Where are reducing agents found in the electrochemical series?

Answer 27

The strongest reducing agents are at the top of the right-hand column of the electrochemical series.

Question 28

What are the steps for balancing an ion electron equation?

Answer 28

1. Balance elements other than oxygen and hydrogen.
2. Balance oxygen by adding water.
3. Balance hydrogen by adding H⁺ ions.
4. Balance the charge by adding electrons.

Question 29

Balance the following: IO₃⁻(aq) → I₂(aq).

Answer 29

2 IO₃⁻(aq) + 12 H⁺(aq) + 10 e⁻ → I₂(aq) + 6 H₂O(l)

Question 30

Balance the following: ClO¯(aq) → Cl¯(aq).

Answer 30

ClO¯ (aq) + 2 H⁺(aq) + 2 e¯ → Cl¯ (aq) + H₂O(l)