NCERT Solution for Class 10 Science Chapter 1
Chemical Reactions and Equations
Exercises Questions
Page No-16
Questions No-16
(a) Oxidation
(b) Reduction
Explain the following in terms of gain or loss of oxygen with two examples each.
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(a) Oxidation: Reaction in which a substance gains oxygen or addition of oxygen or removal of hydrogen in a reaction is called oxidation.
Eg.:
(i) 2Cu + O2 → 2CuO
(ii) 4Al + 3O2 → 2Al2O3
(b) Reduction: Reaction in which a substance looses oxygen or removal of oxygen or gain of hydrogen in a reaction is called reduction.HEg.:
(i) CuO + H2 → Cu + H2O
oxygen is removed from copper oxide so reduction of CuO occurs.
(ii) H2S + Cl2 → 2HCl + S
gain of hydrogen by chlorine gas, so chlorine is reducted to form HCl.
Oxidation – When a substance gains oxygen or loses hydrogen during a reaction, it is called that the substance is oxidized. This phenomenon is called oxidation.
2Cu + O2 –> 2CuO
In this reaction copper gains oxygen and hence is oxidized.
CuO + H2 –> Cu + H2O
In the above reaction hydrogen gains oxygen, and hence oxidized.
Reduction – If a substance loses oxygen or gains hydrogen during a reaction, it is that the substance is reduced. This phenomenon is called reduction.
ZnO + C → Zn + CO
In this reaction zinc loses oxygen, and hence called is reduced.
MnO2+4HCl→MnCl2+2H2O+Cl2
In this reaction Mangnese dioxide loses oxygen and hence is called reduced.