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REDOX REACTIONS
CONCEPT OF OXIDATION & REDUCTION
Oxidation Reduction 
(i) Loss of electron (i) Gain of electron 
(ii) Loss of hydrogen (ii) Gain of hydrogen 
(iii) Gain of oxygen (iii) Loss of oxygen 
(iv) Increase in oxidation number (iv) 
Decrease in oxidation number 
 
OXIDATION NUMBER
Oxidation number change is defined as the change (real or imaginary) which an atom appears to have undergone
when it is present in redox reaction. There are certain rules laid down in order to determine the oxidation number.
(a) Oxidation number of an atom in free elements is zero.
(b) Oxidation number of oxygen is –2, while in peroxides it is –1, in OF
2
 it is +2.
(c) Oxidation number of hydrogen is +1, while in metal hydrides it is –1.
(d) Oxidation number of an ion is equal to the electrical charge present on it.
(e) Oxidation number of group IA elements is +1 and that of group IIA elements is +2.
(f) For complex ions, the algebraic sum of oxidation numbers of all the atoms is equal to the net charge
on the ion.
(g) In case of neutral molecules the algebraic sum of the oxidation number of all the atoms present in the
molecules is zero.
(h) Oxidation number of an atom never be greater than its valence electron. e.g., valence electron for Cr is 6.
Increase in oxidation number of an element in a reaction is known as oxidation while decrease in oxidation
number of an element in a reaction is known as reduction.
Besides +ve and -ve values, fractional values of oxidation number (as average) are also possible.
Balancing of H
2
O can also be done as per the medium given
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FAQs on Quick Revision: Redox Reactions - Chemistry Class 11 - NEET

1. What is a redox reaction?
Ans. A redox reaction, also known as an oxidation-reduction reaction, is a chemical reaction that involves the transfer of electrons between two species. In these reactions, one species loses electrons (undergoes oxidation) while another species gains electrons (undergoes reduction). This transfer of electrons is what drives the reaction.
2. How can you identify a redox reaction?
Ans. There are several ways to identify a redox reaction. One method is to check if there is a change in oxidation states of the elements involved. If an element's oxidation state increases, it has undergone oxidation, while if it decreases, it has undergone reduction. Another way is to look for the presence of a substance gaining or losing oxygen or hydrogen. Additionally, the presence of a transfer of electrons, either directly or through a change in the number of oxygen or hydrogen atoms, indicates a redox reaction.
3. Can you provide an example of a redox reaction in everyday life?
Ans. Sure! A common example of a redox reaction in everyday life is the rusting of iron. When iron reacts with oxygen in the presence of water, it undergoes oxidation, forming iron oxide (rust). The iron loses electrons to oxygen, which gains them, resulting in a redox reaction.
4. How do redox reactions play a role in biological systems?
Ans. Redox reactions are vital in biological systems. They are involved in processes such as cellular respiration, where glucose is oxidized to produce energy in the form of ATP. During this process, electrons are transferred from glucose to oxygen, resulting in the release of energy. Redox reactions also play a role in photosynthesis, where light energy is used to convert carbon dioxide and water into glucose, releasing oxygen in the process.
5. What are some applications of redox reactions in industry?
Ans. Redox reactions have various applications in industry. One example is in the production of metals, such as aluminum. The extraction of aluminum from its ore involves a redox reaction, where aluminum oxide is reduced to aluminum using a powerful electric current. Redox reactions are also used in the production of chemicals, such as in the synthesis of ammonia through the Haber process, where nitrogen gas is reduced by hydrogen gas.
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