What Is a Redox Reaction Definition Oxidation Reduction Rules Types and Balanced Equation Examples
What is Redox Reaction
Many chemical reactions involve transfer of electrons from one chemical substance to another. These electron transfer reactions are termed as oxidation-reduction or Redox reaction, or those reactions which involve oxidation and reduction both simultaneously are known as oxidation and reduction/ Redox reaction. Redox reaction can also be termed as an increase in oxidation number or decrease in oxidation number simultaneously.
Oxidation and Reduction
There are mainly four four concepts of oxidation and reduction reaction:
A. Classical Concept: According to this concept, oxidation and reduction can be explained as:
Oxidation
Oxidation is a process which involves:
Addition of oxygen
Removal of hydrogen
Addition of electronegative elements
Removal of electropositive elements
Increment in oxidation state of electropositive element.
Reduction
Reduction is a process which involves:
Removal of oxygen
Addition of hydrogen
Removal of electronegative elements
Addition of electropositive elements
Decrement in oxidation state of electropositive elements
B. Modern Concept or Electronic Concept
Oxidation
According to this concept the process which involves the loss of one or more electrons from an atom or an ion or molecules is called oxidation.
Reduction
According to this concept, the process which involves gain of one or more electrons by an atom or ion molecule is called reduction.
C. Valency Concept of Oxidation and Reduction
Oxidation
According to this concept, it is the process in which increase in positive valency or decrease in negative valency of a substance takes place called oxidation.
Reduction
According to this concept,it is the process in which decrease in positive or increase in negative charge of a substance takes place called reduction.
D. Oxidation Number Concept
Oxidation
According to this concept, the oxidation number of elements increases.
Reduction
According to this concept oxidation number of elements decreases.
Oxidising Agent or Oxidants
The Substance which accept electrons in a chemical reaction i.e electron acceptors are oxidising agents:
Oxidising agents are lewis acid.
Substance which can oxidise others and reduce themselves.
Substance which shows decrement in oxidation number.
All high electronegative elements like N, O, F, Cl, etc are oxidants.
All metallic oxides are oxidants.
Some non metallic oxides are also oxidants like CO2, CaO, etc.
Reducing Agents or Reductant
The substances which donate electrons in a chemical reaction are reducing agents i.e electron donors are reducing agents.
Reducing agents are Lewis base.
Substances which can reduce others and oxidise themselves.
Substance which shows decrement in oxidation number.
All metal like K, Mg, Ca, etc are examples of reductants.
All metallic hydrides are examples of reductants.
All hydro acids are reductants. Example: HF, HCl, HBr, etc.
Oxidation Number
It represents the number of electrons gained or lost by an atom when it changes in compound from free state. It is also defined as charge on an atom when the atom is in combining state.
If electrons are gained by an atom in the formation of compounds the oxidation number is given a negative sign.
If electrons are loose by atom in the formation of compounds the oxidation number is given a positive sign.
It represents real charge in case of ionic compounds and imaginary charge in case of covalent compounds.
Maximum oxidation number is equal to the group number in the periodic table.
Minimum number of oxidation states is equal to group number i.e (-8).
Oxidation State
Oxidation state of an atom is defined as the oxidation number per atom for all practical purposes. Oxidation state is often expressed as the oxidation number.
Types of Redox Reactions
Intermolecular Redox Reaction
When oxidation and reduction take place separately in the different compounds called intermolecular redox reactions.
SnCl2+ 2FeCl3-------SnCl4+2FeCl2
Intramolecular Redox Reaction
During chemical reaction if oxidation and reduction take place in a single compound then reaction is called intramolecular redox reaction.
2KClO3------KCl+3O2
Disproportionation Reaction
When reduction and oxidation take place on the same elements of the compound is called disproportionation reaction.
H2O2--------H2O+3O2
Multiple Choice Questions
1. Oxidation number of nitrogen in NH2OH:
0
+1
-1
-2
Answer: (C)
2. Which one has same oxidation state in all of its compound:
Hydrogen
Fluorine
Carbon
Oxygen
Answer: (b)
3. Oxidation number of C in HCN:
+2
-3
+3
Zero
Answer: (a)
4. If elements is in lowest oxidation state under proper condition it act as a:
Reducing agent
An Oxidising agent
Both of them
None of them
Answer: (a)
FAQs on Redox Reaction Oxidation and Reduction Explained Clearly
1. What is a redox reaction in chemistry?
A redox reaction is a chemical reaction in which one substance is oxidized (loses electrons) and another is reduced (gains electrons) simultaneously. In every redox reaction, electron transfer occurs between species.
- Oxidation = loss of electrons
- Reduction = gain of electrons
- Both processes occur at the same time
2. What is the difference between oxidation and reduction?
The difference between oxidation and reduction is that oxidation involves loss of electrons while reduction involves gain of electrons.
- Oxidation: Increase in oxidation number, loss of electrons, or gain of oxygen
- Reduction: Decrease in oxidation number, gain of electrons, or loss of oxygen
3. How do you identify a redox reaction?
A reaction is a redox reaction if there is a change in oxidation numbers of elements between reactants and products. To identify it:
- Assign oxidation numbers to each element.
- Check for increase (oxidation) or decrease (reduction).
- If both occur, it is a redox reaction.
4. What is an oxidizing agent and a reducing agent?
An oxidizing agent is a substance that gains electrons and causes oxidation, while a reducing agent loses electrons and causes reduction.
- Oxidizing agent is reduced.
- Reducing agent is oxidized.
5. How do you balance a redox reaction using the half-reaction method?
The half-reaction method balances redox reactions by separating oxidation and reduction processes and balancing electrons. Steps:
- Split the reaction into oxidation and reduction half-reactions.
- Balance atoms other than O and H.
- Balance O with H2O and H with H+ (acidic medium).
- Balance charge with electrons.
- Equalize electrons and add the half-reactions.
6. What are some common examples of redox reactions?
Common redox reaction examples include combustion, rusting, and displacement reactions.
- Combustion: CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
- Rusting: 4Fe(s) + 3O2(g) → 2Fe2O3(s)
- Displacement: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
7. What is the oxidation number in a redox reaction?
The oxidation number is the hypothetical charge assigned to an atom in a compound assuming complete electron transfer. It helps track electron movement in redox reactions.
- Free elements have oxidation number 0.
- Oxygen is usually −2.
- Hydrogen is usually +1 (except in metal hydrides).
8. Is combustion a redox reaction?
Yes, combustion is a redox reaction because oxygen is reduced and the fuel is oxidized. During combustion:
- The fuel loses electrons (oxidation).
- Oxygen gains electrons (reduction).
9. What is disproportionation in redox reactions?
A disproportionation reaction is a redox reaction in which the same element is simultaneously oxidized and reduced. One species forms two products with different oxidation states.
- One atom increases oxidation number.
- Another atom decreases oxidation number.
10. Why are redox reactions important in everyday life?
Redox reactions are important because they drive essential processes like energy production, corrosion, and industrial chemistry. Key applications include:
- Cellular respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O
- Batteries and electrochemical cells (electricity generation)
- Metal extraction from ores
- Rusting and corrosion processes
