Chemical reactions and equations class 10
Introduction-
Chemical reactions are the process in which new substances having new properties are formed.
Chemical equations-
The method of representing a chemical reaction by the symbols of elements and formulae of compounds involved in it is called chemical equation or it is important to know that a chemical equation is a short-hand method to represent a chemical reaction.
Unbalanced chemical equation-
An unbalanced chemical equation written in the form of symbols and formulae is called skeletal or unbalanced equation. In unbalanced chemical equation, number of atoms of each type in reactant side (LHS) is not equal to number of atoms in product side (RHS).
Note- some important facts about skeletal equations:
(1) An unbalanced chemical equation contain unequal number of some or all atom of the reactants and products.
(2) According to the law of conservation of mass, "matter can neither be created nor destroyed" Thus, the total number of all the atoms on both the sides of the chemical equation must be equal. Since it is not true for an unbalanced chemical equation, therefore skeletal equation is against the law of conservation of mass.
Balanced chemical equation-
A chemical equation having equal number of all the atoms in the reactants and products is called balanced chemical equation.
Some facts about a balanced chemical equation:
1. A balanced chemical equation has equal number of all the atoms on both sides of the chemical equation.
2. A balanced chemical equation confirms the law of conservation of mass in chemical reactions.
3. The total mass of all the reactants is equal to the total mass of all the products.
Note- before balancing a chemical equation, it should be kept in mindthat symbol of an element or formula of a compound should never be changed. The elements such as hydrogen oxygen nitrogen fluorine chlorine bromineand iodine exist as diatomic molecules for balancing the equation.
The word equation is written first in the form of chemical equation and then it is balanced by hit and trial method. It is important to know that 2H2 and 4HCL both contain equal numbers 4 of H atoms. H2so4and 2NAOH contain equal number (2) of H-atoms, 2ALCL3 and 6hclcontain equal number (6) of cl-atoms.
