Question

Give reason why a chemical equation needs to be balanced?

Answer 1

Balanced chemical equation represents the equal number of atoms on both reactants and product side.

Complete step by step answer:
We know that chemical reaction is the process in which one or more substances [Reactants] gets converted to other substances [products]. In a chemical reaction, the reactant atoms rearrange to create different substances as products. The chemical reactions are mainly of a type:
(i) Combination/synthesis reaction: it is a type of chemical reaction in which two or more chemical compounds i.e. reactants, give a single new compound/substance. Since reactants get combined. So, it is called a combination reaction. Begins general representation: -
(a) $A + B \to AB$ [A and B are reactants and AB is product]

(ii) Decomposition Reaction: It is a converse of combination reaction. In this reaction, a single substance breaks down into two or more simple substances.
It can be generally represented as
$AB \to A + B$ Decomposition usually takes place by heating or treating it with a chemical compound.
(iii) Displacement reaction: It is a type of reaction in which more reaction element replaces less reactive element from its salt solution. This reaction is also known as a replacement reaction.
(b) For e.g. $A + BC({\text{Reactants)}} \to AB + C{\text{(Products)}}$

(iv) Conclusion reaction: It is a chemical reaction in which a substance reacts with oxygen gas, releasing energy in the form of heat and light.
For eg.
$2Mg + {O_2} \to 2MgO$
The chemical reaction needs to be balanced in order to follow the law of conservation of mass which states that a mass can never be created nor be destroyed in a chemical reaction. So the mass on both reactant side and product side should be equal. This can be done by balancing atoms on the both side of a chemical reaction. That’s why a chemical equation needs to be balanced. Moreover chemical equation needs to be balanced to establish role relationship which is needed for stoichiometric calculation.

Note:
Displacement reaction are further of two types:
(i) Single Replacement reaction: It is reaction which occurs when one element replaces another element is one compound e.g. $A + BC \to AB + C$
(ii) Double Replacement Reaction: It is a reaction which occurs when two ionic compound exchange ions, producing two new iconic compounds i.e. $AB + CD \to AD + BC$