Unit 1: KA3 Oxidising and reducing agents

Question 1

REDUCTION?

Answer 1

Gain of electrons by a reactant in any reaction

Question 2

OXIDATION?

Answer 2

Loss of electrons by a reactant in any reaction

Question 3

In a redox reaction, when does reduction and oxidation take place?

Answer 3

They take place at the same time

Question 4

What is an OXIDISING agent?

Answer 4

A substance that ACCEPTS electrons

Question 5

What is a REDUCING agent?

Answer 5

A substance that DONATES electrons

Question 6

What can be identified in redox reactions?

Answer 6

The OXIDISING and REDUCING agents

Question 7

Elements with — electronegativities tend to form ions by LOSING electrons (forming ——– ions) and so…

Answer 7

LOW.
positive,
act as reducing agents.

Question 8

Elements with —- electronegativities tend to form ions by GAINING electrons (forming ——– ions) and so…

Answer 8

HIGH.
negative,
act as oxidising agents.

Question 9

Which group in the periodic table will you find the strongest reducing agents?

Answer 9

Group 1

Question 10

Which group in the periodic table will you find the strongest oxidising agents?

Answer 10

Group 7

Question 11

Compounds, group ions and molecules can act as oxidising or reducing agents. These include:
1) Hydrogen peroxide is a molecule that is…
2) Dichromate and permanganate ions are group ions that are strong…
3) Carbon monoxide is a gas that can be used as a…

Answer 11

1) Hydrogen peroxide = an OXIDISING agent
2) Dichromate and permanganate ions = strong OXIDISING agents in acidic solutions.
3) Carbon monoxide = a REDUCING agent

Question 12

Oxidising agents are widely used because…

Answer 12

They can KILL FUNGI AND BACTERIA EFFECTIVELY,
&
They can INACTIVATE VIRUSES.

Question 13

The oxidation process is also an effective means of…

Answer 13

Breaking down coloured compounds –> making oxidising agents ideal for use as ‘bleach’ for clothes and hair.

Question 14

What does the ELECTROCHEMICAL SERIES represent?

Answer 14

It represents a series of reduction reactions.

Question 15

Where are the STRONGEST OXIDISING AGENTS (with regards to the electrochemical series)?

Answer 15

At the bottom of the left-hand column of the electrochemical series.

Question 16

Where are the STRONGEST REDUCING AGENTS (with regards to the electrochemical series)?

Answer 16

At the top of the right-hand column of the electrochemical series.

Question 17

How can an ion-electron equation be balanced?

Answer 17

By adding appropriate numbers of WATER molecules, HYDROGEN IONS and ELECTRONS.

Question 18

Ion-electron equations can be combined to produce…

Answer 18

REDOX EQUATIONS.

Question 19

An oxidising agent ——– something else.
The oxidising agent itself is ——- and ——- electrons.
OXIDISING AGENTS TENDS TO BECOME MORE ——–.

Answer 19

OXIDISES,
REDUCED,
accepts/gains,
NEGATIVE.

Question 20

A reducing agent ——- something else.
The reducing agent itself is ——– and —– electrons.
REDUCING AGENTS TEND TO BECOME MORE ——–.

Answer 20

REDUCES,
OXIDISED,
loses,
POSITIVE.

Question 21

What is acidified permanganate solution an example of?
MnO₄⁻+ 8H⁺ + 5e⁻ –> Mn²⁺ + 4H₂O

Answer 21

An oxidising agent which gains electrons.

Question 22

What are sulphite ions an example of?
SO₃²⁻ + H₂O –> SO₄²⁻ + 2H⁺ + 2e⁻

Answer 22

A reducing agent which loses electrons.

Question 23

Electronegativity can be used to…

Answer 23

predict which elements lose or gain electrons when they form ions.

Question 24

Does Potassium accept/lose electrons?

Answer 24

They lose electrons because they have a low electronegativity value (0.8)
K –> K⁺ + e⁻

Question 25

Does Lithium accept/lose electrons?

Answer 25

They lose electrons because they have a low electronegativity value (1.0). Li --> Li⁺ + e⁻

Question 26

Does Chlorine accept/lose electrons?

Answer 26

They accept electrons because they have a high electronegativity value (3.0). Cl + e⁻ --> Cl⁻

Question 27

Does Fluorine accept/lose electrons?

Answer 27

They accept electrons because they have a high electronegativity value (4.0). F + e⁻ --> F⁻

Question 28

Group 1 elements are the weakest reducing agents. True or False? Where are the strongest REDUCING agents located in the Electrochemical Series?

Answer 28

False, Group 1 elements are the STRONGEST reducing agents. They're found at the top of the right-hand column of the electrochemical series.

Question 29

Group 7 elements are the strongest oxidising agents. True or False? Where are the strongest OXIDISING agents located in the Electrochemical Series?

Answer 29

True. At the bottom left of the electrochemical series.

Question 30

Acidified peroxide is an oxidising agent as it...

Answer 30

accepts electrons and is reduced itself.

Question 31

Acidified dichromate is an oxidising agent as it...

Answer 31

accepts electrons and is reduced itself.

Question 32

Carbon monoxide is a reducing agent as it...

Answer 32

loses electrons and is oxidised itself.

Question 33

If the reduction reaction in electrochemical series is reversed, it becomes an...

Answer 33

Oxidation reaction

Question 34

When given the reactant and product species, how do you write ion-electron equations?

Answer 34

1) Write down the main species involved in the reaction: IO₃⁻ --> I₂ 2) Balance all atoms except O and H: 2IO₃⁻ --> I₂ 3) Add H₂O to other side to balance O atoms: 2IO₃⁻ --> I₂ + 6H₂O 4) Add H⁺ ions to other side to balance H atoms: 2IO₃ + 12H⁺ --> I₂ + 6H₂O 5) Add e⁻ to most positive side to balance charge: 2IO₃ + 12H⁺ + 10e⁻ --> I₂ + 6H₂O

Question 35

Can ion-electron equations be combined to produce redox equations?

Answer 35

Yes

Question 36

Combine the reduction equation for Iodine and the oxidation equation for S₄O₆ for your REDOX reaction equation!

Answer 36

REDUCTION EQUATION: I₂ + 2e⁻ --> 2I⁻ OXIDATION EQUATION (flip equation): 2S₂O₃²⁻ --> S₄O₆²⁻ + 2e⁻ (balance out electrons) REDOX REACTION: I₂ + 2S₂O₃²⁻ --> S₄O₆²⁻ + 2I⁻ (get rid of the electrons)

Question 37

Where the electrons don't cancel out, ion-electron equations may have to be multiplied. How do you do this?

Answer 37

EXAMPLE: 1) MnO₄⁻ + 8H⁺ + 5e⁻ --> Mn²⁺ + 4H₂O Fe²⁺ --> Fe³⁺ + e⁻ 2) Balance the electrons by multiplying: MnO₄⁻ + 8H⁺ + 5e⁻ --> Mn²⁺ + 4H₂O 5Fe²⁺ --> 5Fe³⁺ + 5e⁻ 3) Cancel the electrons out. ---> 5e⁻ 4) MnO₄⁻ + 8H⁺ + 5Fe²⁺ --> Mn²⁺ + 4H₂O + 5Fe³⁺

Question 38

Oxidising agents will be -------. Reducing agents will be --------.

Answer 38

Reduced. Oxidised.

Question 39

Fluorine with an electronegativity value of 4.0 will be a strong reducing agent. True or False?

Answer 39

False, Fluorine will be a strong OXIDISING agent, and so will itself be reduced (due to its strong attraction for electrons).

Question 40

Some metals are more reactive than others (refer to the reactivity series). In an experiment, a strip of metal is added to a solution of another. If the metal is MORE REACTIVE than the metal in solution, this metal...

Answer 40

displaces (pushes out) the less reactive solution.

Question 41

A metal higher in the series? Metal atoms will be --------. They are the -------- agent. Zn and Cu Redox Experiment. Write the oxidation equation for the reducing agent.

Answer 41

OXIDISED. REDUCING eg. Zn --> Zn²⁺ + 2e⁻

Question 42

A metal lower in the series? Metal ions will be -------. Metal ions are the --------- agent. Zn and Cu Redox Experiment. Write the reduction equation for the oxidising agent.

Answer 42

REDUCED. OXIDISING eg. Cu²⁺ + 2e⁻ --> Cu

Question 43

Potassium permangate is used in...

Answer 43

fish ponds to treat common fish pathogens such as gill parasites and external bacterial and fungal infections.

Question 44

You can use diluted potassium permanganate to...

Answer 44

treat athlete's foot (a fungal infection) in humans.

Question 45

Hydrogen peroxide oxidises...

Answer 45

coloured pigments in hair (related to melanin) to colourless substances

Question 46

How does Chlorine in swimming pools work?

Answer 46

Chlorine breaks down into many different chemicals, including hypochlorous acid (HOCL). The hypochlorous acid is a strong oxidising agent and kills microorganisms by removing electrons from the bacteria --> destroying the cell walls and enzymes and structures inside the cell, rendering them harmless.

Question 47

Sodium hypochlorite acts as a...

Answer 47

- powerful disinfectant. In solution, the hypochlorite ions from hypochlorous acid, HClO. This is the oxidising agent. Household bleach is, in general, a solution containing 4-6% sodium hypochlorite.

Question 48

CO (carbon monoxide) is a

Answer 48

strong reducing agent and reduces metal oxides to form metals.