Redox Reactions - Applications

1. Applications of Redox Reaction in Electrochemistry

The redox reaction mechanism is used to release electrical energy from a battery that generates
a direct current. Our daily lives, which rely on redox processes, use batteries, also referred to as
electrochemical cells. For instance, the most simple example is the button cells or dry cells
which are used in our remote controls, clocks and watches.

Daniell cell is an example of a galvanic cell or electrochemical cell, which converts chemical
energy into electrical energy. Copper ions are reduced at the cathode and zinc ions are oxidised
at the anode in the Daniell cell.

Half-cell reaction at the anode: Zn(s) --> Zn2+(aq) + 2e- |

As zinc loses the electron, hence at the anode, oxidation occurs.

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Half-cell reaction at the cathode: Cu2+ (aq) + 2e- Cu(s)
As Copper gains the electron, hence at the cathode, reduction occurs.

Half-cell reaction at the anode: Zn(s) --> Zn2+(aq) + 2e-

Half-cell reaction at the cathode: Cu2+(aq) + 2e- --> Cu(s)
Overall reaction: Zn(s) + Cu2+(aq) --> Zn2+(aq) + Cu(s)

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When a zinc rod is dipped in copper sulphate (CuSO4) solution, we can see that after some time
solid copper gets deposited over the zinc rod and the zinc from the zinc rod gets converted into
zinc sulphate (ZnSO4). This is indicated by the change in colour of the solution from blue to
transparent.

The aforementioned reaction can be represented as

2. Application of Redox Reaction in Combustion

Combustion falls within the category of an oxidation-reduction reaction, making it a redox

reaction. An explosion is a form of combustion and is typically classified as a redox reaction.
Space rockets use redox reactions as their internal mechanism. An oxidation-reduction reaction
results from the mixture of ammonium perchlorate and powdered aluminium inside the rocket
boosters. The aluminium powder acts as the fuel and ammonium perchlorate acts as the
oxidiser.

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For example, the combustion of methane can be expressed using the chemical equation given
below.

CH4(g) + 2O2(g) --> CO2(g) + 2H2O(g)

Oxygen (O2) is reduced and the other elements carbon and hydrogen are oxidised during
combustions. O2 is the most common oxidising agent on Earth due to its abundance in the
atmosphere.

3. Redox Reaction in Photosynthesis applications

Photosynthesis is the conversion of water and carbon dioxide into carbohydrates in green
plants.

The reaction involved is

In the aforementioned reaction, it can be seen that the water molecules are oxidised to oxygen
while the carbon dioxide is brought down to carbohydrates, forming a redox reaction. Sunlight
provides the necessary heat energy for this reaction to take place. An important source of
nourishment for both plants and animals is provided by this reaction.

4. Redox Reaction in Photographic Films

Silver bromide is used in photography as a component of an emulsion that aids in the

development of a photographic image. Because the grains of silver bromide are light-sensitive
and suspended in gelatin, they can be used to make photographic emulsions. Silver bromide
breaks down when exposed to light, which helps to preserve photographs.

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Uses of Redox Reactions in Daily Life

1. Redox reactions are used in the electroplating process to apply a thin layer of a substance to
an item. Gold-plated jewellery is made using an electroplating process.

2. Electrolysis, which is dependent on redox processes, is used to purify metals.

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3. Additionally, oxidation-reduction reactions are used to sanitize water and bleach materials.

4. Redox reactions are used in the production of many chemicals, including chlorine and caustic
soda.

5. By attaching them to sacrificial anodes, which go through corrosion instead, many metal
surfaces can be shielded against corrosion. The galvanization of steel is a typical illustration of
this method.

6. In order to produce cleaning goods, enterprises use the oxidation process.

7. The oxidation reaction of ammonia results in the production of nitric acid, which is a
component of many fertilisers.

8. Alcohol absorption into the bloodstream is correlated with alcohol concentration in alveolar
air. The oxidising agents in the gadget oxidise the ethanol present in the breath when the user
breathes into it.

The reaction involved is given as follows

Practice Problems

Q1. Pick out the redox reaction among the given reactions?

1. NaOH(aq) + HCl(aq) --> NaCl(s) + H2O(aq)

2. AgNO3(aq) + NaCl(aq) --> AgCl(|) + NaNO3(aq)

3. 2NaCN(aq) + H2SO4(aq) --> 2HCN(aq) + Na2SO4(aq)

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 4. Zn(s) + CuSO4(aq) --> ZnSO4(aq) + Cu(s)

Answer: D)

Solution: A chemical reaction in which the oxidation number of a participating chemical species
changes is referred to as an oxidation-reduction reaction or redox reaction.

In option A, there is no change in the oxidation state of any element, indicating that no
oxidation or reduction is occurring here. This indicates that this is not a redox reaction.Na(+1 ),
H(+1), Cl(-1), O(-2) remains the same after the reaction.

In option B, no element's oxidation state changes, indicating that no oxidation or reduction is

taking place. This indicates that the reaction is not redox in nature.

Ag(+1 ), H(+1), Cl(-1), O(-2), N(+5) remains the same after the reaction.

In option C, no element's oxidation state alters, proving that neither oxidation nor reduction is
occurring. This suggests that the reaction is not a redox reaction.

Ag(+1 ), H(+1), Cl(-1), O(-2), S(+6) that remains the same after the reaction.

In option D, there is clearly a change in the oxidation states of Zn and Cu which involve oxidation
and reduction simultaneously. Hence, this given reaction is a redox reaction.

So, option D) is the correct answer.

Q2. Pick out the non-redox reaction among the given reactions?\

1. CuO(s) + H2(g) --> Cu(s) + H2O(aq)

2. P4 --> PH3 + H2PO2-

3. HNO3(aq) + CuO(s) --> Cu(NO3)2(aq) + H2O(aq)

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 4. FeCl3(aq) + HCl(aq) --> HFeCl4(aq)

1. 1) and 3)

2. 1) and 2)

3. 2) and 4)

4. 3) and 4)

Answer: D)

Solution: A chemical reaction in which the oxidation number of a participating chemical species
changes is referred to as an oxidation-reduction reaction or redox reaction.

In reaction 1), there is clearly a change in oxidation states of H and Cu which involve oxidation
and reduction simultaneously. Hence, the given reaction is a redox reaction.

Reduction: CuO (2+2) --> Cu (0);

Oxidation: H2(0) --> H2O (+1)

In reaction 2), there is clearly a change in the oxidation states of P, which involve both oxidation
and reduction. As a result, the given reaction is a redox reaction.

Reduction: P4(0) --> PH3(-3);

Oxidation: P4(0) --> H2PO2- (+1)

In reaction 3), no element's oxidation state changes, indicating that no oxidation or reduction is
taking place. This indicates that the reaction is not redox in nature.

The oxidation states of the elements [ H(+1), Cu(+2), O(-2), N(+5)] remains the same after the
reaction.

In reaction 4), no element's oxidation state alters, proving that neither oxidation nor reduction
is occurring. This suggests that the reaction is not a redox reaction

The oxidation states of the elements [ H(+1), Cl(-1), Fe(+3)] remains the same after the
reactions.

Hence, options 3) and 4) are non-redox reactions.

So, option D) is the correct answer.

Q3. Which of the following is an only oxidising agent?

1. H2SO4

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 2. H2S

3. SO2

4. Both (A) and (C)

Answer: A)

Solution:

In option (A), S in H2SO4 is in the highest oxidation state (+6). So, S can accept electrons and exist
in lower oxidation states (+4, +2, -2). Hence, it behaves as an oxidising agent.

In option (B), S in H2S is in the lowest oxidation state (-2). So, S can donate electrons and exist in
higher oxidation states (+4, +2, +6). Hence, it behaves as a reducing agent.

In option (C), S in SO2 is in an intermediate oxidation state (+4). So, S can either donte electrons
and exist in a higher oxidation state (+6) or can accept electrons and exist in lower oxidation
states (+2, -2). Hence, it behaves either as a reducing agent or as an oxidising agent.

So, option A) is the correct answer.

Q4. Which of the following statements is correct about redox reactions?

1. In redox processes, reducing agents are electron-accepting species that experience a

decrease in oxidation state.

2. The electroplating of various metals on jewellery is a redox reaction application.

3. In redox processes, oxidising agents are electron-donating substances that donate excess
electrons and experience an increase in oxidation state.

4. All of these

Answer: A)

Solution: Statement B is true as electroplating by the electrolytic cell is an application of redox

reactions.

Electron-accepting species that experience a decrease in oxidation state are called oxidising
agents. Electron-donating substances that donate excess electrons and experience an increase
in oxidation state are called reducing agents. Hence, statements A and C are incorrect.

So, option B) is the correct answer.

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Frequently Asked Questions - FAQ

Question 1. Is cellular respiration a reduction or an oxidation reaction?

Answer. Cellular respiration is a redox reaction. Respiration is a set of metabolic reactions that
involve both electron loss and gain. As a result, it is known as an oxidation-reduction or redox
reaction. In this context, oxidation refers to electron loss, while reduction refers to electron
gain.

Question 2. Is it true that every chemical reaction is a redox reaction?

Answer. No, not all chemical reactions are redox in nature. Non-redox reactions include acid-
base neutralisation reactions, double decompositions, and precipitation reactions.

Question 3. Why is redox important to understand?

Answer. Redox reactions lead us down a crucial conceptual path in chemistry. Our
understanding of redox begins with oxygen gain and loss and develops into hydrogen gain and
loss. This paves the way for understanding all chemical reactions as electron rearrangements.

Question 4. What happens if oxidation does not occur in nature?

Answer. There will be no life if there is no oxidation because it affects all metabolic reactions
that occur in nature. The process of reacting to different substances with oxygen is known as
oxidation.

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