Unit 1: KA3 Oxidising and reducing agents Flashcards
REDUCTION?
Gain of electrons by a reactant in any reaction
OXIDATION?
Loss of electrons by a reactant in any reaction
In a redox reaction, when does reduction and oxidation take place?
They take place at the same time
What is an OXIDISING agent?
A substance that ACCEPTS electrons
What is a REDUCING agent?
A substance that DONATES electrons
What can be identified in redox reactions?
The OXIDISING and REDUCING agents
Elements with — electronegativities tend to form ions by LOSING electrons (forming ——– ions) and so…
LOW.
positive,
act as reducing agents.
Elements with —- electronegativities tend to form ions by GAINING electrons (forming ——– ions) and so…
HIGH.
negative,
act as oxidising agents.
Which group in the periodic table will you find the strongest reducing agents?
Group 1
Which group in the periodic table will you find the strongest oxidising agents?
Group 7
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…
1) Hydrogen peroxide = an OXIDISING agent
2) Dichromate and permanganate ions = strong OXIDISING agents in acidic solutions.
3) Carbon monoxide = a REDUCING agent
Oxidising agents are widely used because…
They can KILL FUNGI AND BACTERIA EFFECTIVELY,
&
They can INACTIVATE VIRUSES.
The oxidation process is also an effective means of…
Breaking down coloured compounds –> making oxidising agents ideal for use as ‘bleach’ for clothes and hair.
What does the ELECTROCHEMICAL SERIES represent?
It represents a series of reduction reactions.
Where are the STRONGEST OXIDISING AGENTS (with regards to the electrochemical series)?
At the bottom of the left-hand column of the electrochemical series.
Where are the STRONGEST REDUCING AGENTS (with regards to the electrochemical series)?
At the top of the right-hand column of the electrochemical series.
How can an ion-electron equation be balanced?
By adding appropriate numbers of WATER molecules, HYDROGEN IONS and ELECTRONS.
Ion-electron equations can be combined to produce…
REDOX EQUATIONS.
An oxidising agent ——– something else.
The oxidising agent itself is ——- and ——- electrons.
OXIDISING AGENTS TENDS TO BECOME MORE ——–.
OXIDISES,
REDUCED,
accepts/gains,
NEGATIVE.
A reducing agent ——- something else.
The reducing agent itself is ——– and —– electrons.
REDUCING AGENTS TEND TO BECOME MORE ——–.
REDUCES,
OXIDISED,
loses,
POSITIVE.
What is acidified permanganate solution an example of?
MnO₄⁻+ 8H⁺ + 5e⁻ –> Mn²⁺ + 4H₂O
An oxidising agent which gains electrons.
What are sulphite ions an example of?
SO₃²⁻ + H₂O –> SO₄²⁻ + 2H⁺ + 2e⁻
A reducing agent which loses electrons.
Electronegativity can be used to…
predict which elements lose or gain electrons when they form ions.
Does Potassium accept/lose electrons?
They lose electrons because they have a low electronegativity value (0.8)
K –> K⁺ + e⁻
Does Lithium accept/lose electrons?
They lose electrons because they have a low electronegativity value (1.0).
Li –> Li⁺ + e⁻
Does Chlorine accept/lose electrons?
They accept electrons because they have a high electronegativity value (3.0).
Cl + e⁻ –> Cl⁻
Does Fluorine accept/lose electrons?
They accept electrons because they have a high electronegativity value (4.0).
F + e⁻ –> F⁻
Group 1 elements are the weakest reducing agents. True or False?
Where are the strongest REDUCING agents located in the Electrochemical Series?
False, Group 1 elements are the STRONGEST reducing agents.
They’re found at the top of the right-hand column of the electrochemical series.
Group 7 elements are the strongest oxidising agents. True or False?
Where are the strongest OXIDISING agents located in the Electrochemical Series?
True.
At the bottom left of the electrochemical series.
Acidified peroxide is an oxidising agent as it…
accepts electrons and is reduced itself.
Acidified dichromate is an oxidising agent as it…
accepts electrons and is reduced itself.
Carbon monoxide is a reducing agent as it…
loses electrons and is oxidised itself.
If the reduction reaction in electrochemical series is reversed, it becomes an…
Oxidation reaction
When given the reactant and product species, how do you write ion-electron equations?
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
Can ion-electron equations be combined to produce redox equations?
Yes
Combine the reduction equation for Iodine and the oxidation equation for S₄O₆ for your REDOX reaction equation!
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)
Where the electrons don’t cancel out, ion-electron equations may have to be multiplied. How do you do this?
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⁺
Oxidising agents will be ——-.
Reducing agents will be ——–.
Reduced.
Oxidised.
Fluorine with an electronegativity value of 4.0 will be a strong reducing agent. True or False?
False, Fluorine will be a strong OXIDISING agent, and so will itself be reduced (due to its strong attraction for electrons).
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…
displaces (pushes out) the less reactive solution.
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.
OXIDISED.
REDUCING
eg. Zn –> Zn²⁺ + 2e⁻
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.
REDUCED.
OXIDISING
eg. Cu²⁺ + 2e⁻ –> Cu
Potassium permangate is used in…
fish ponds to treat common fish pathogens such as gill parasites and external bacterial and fungal infections.
You can use diluted potassium permanganate to…
treat athlete’s foot (a fungal infection) in humans.
Hydrogen peroxide oxidises…
coloured pigments in hair (related to melanin) to colourless substances
How does Chlorine in swimming pools work?
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.
Sodium hypochlorite acts as a…
- 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.
CO (carbon monoxide) is a
strong reducing agent and reduces metal oxides to form metals.
