Question

What is a chemical equation? Give examples.

Answer 1

Chemical reactions are the chemical changes in which reactants transform into products by bond-making or bond-breaking or both between different atoms or molecules. When such a reaction is expressed in terms of symbols and formula, it gives us chemical equations.

Complete step-by-step answer:
A chemical equation is a chemical reaction which is expressed in chemical formulas to identify the reactants and products. The symbols used to express a chemical equation are the chemical codes for an element. Each element has either one or two letter atomic symbols, which is an abbreviated form of its name or source.
Representation of a chemical reaction in terms of symbols and chemical formula of the reactants and products taking part in the reaction is known as a chemical equation.
For example, $N{H_3} + HCl \to N{H_4}Cl$, in this reaction ammonia and hydrochloric acid is reacting to form ammonium chloride.
For solids, it is denoted by (s).
For liquids, it is denoted by (l)
For gases it is denoted by(g)
For aqueous, the symbol is (aq)
For gas produced in the reaction it is shown by ($\uparrow$)
For precipitate formed during a reaction, it is ($\downarrow$)
For example, $Zn(s) + {H_2}S{O_4}(aq) \to ZnS{O_4}(aq) + {H_2}( \uparrow )$, in this reaction the symbols are placed to show the state of atom or compound when the reaction is taking place.
If one or more new substances with new chemical and physical properties are formed, it is known as chemical change. For example, when copper sulphate reacts with iron, the new substances formed are ferrous sulphate and copper. When change in colour or state occurs but no new substance is formed, it is known as physical change. For example, when water changes to steam on boiling, no new substance is formed.
The total mass of the products formed in a chemical reaction is equal to the total mass of the reactant that took part in a chemical reaction. Such a reaction is called a balanced chemical equation.
${H_2} + C{l_2} \to 2HCl$

Note: When these chemical equations are written in word format, they are referred to as word equations. For example, magnesium + oxygen $\to$ magnesium oxide. And phase change reactions are not chemical reactions, they are just physical changes such as from ice to water or water to vapour.