Question

What is a neutralisation reaction? Give two examples.

Answer 1

Neutralisation reactions are in which acid and base react to form salt and water. Neutralisation reactions have many applications. The type of salt formed will depend upon the acid and base reacted.

Complete step by step answer:
Neutralisation reactions are basically an acid-base reaction. An acid reacts with an equimolar amount of base to give corresponding salt and water. The proton liberated by acid will combine with hydroxide ion liberated by base to form water. The ions left will then combine to form salt.
Example- $1$: Reaction of HCl with NaOH-
HCl is a strong acid and NaOH is a strong base. Hence they dissociate as,

HCl \to {H^ + } + C{l^ - } \\\ NaOH \to N{a^ + } + O{H^ - } $$ The proton and hydroxide ion combines to form water and sodium ion and chloride ion then combines to form sodium chloride salt. $ {H^ + } + O{H^ - } \to {H_2}O \\\ N{a^ + } + C{l^ - } \to NaCl $ In brief, the overall reaction can be written as, $$HCl + NaOH \to {H_2}O + NaCl$$ Example-$2$: Sulphuric acid reacts with potassium hydroxide to give water and potassium sulphate. Sulphuric acid is a strong acid and potassium hydroxide is a strong base. Their dissociation can be written as,

{H_2}S{O_4} \to 2{H^ + } + S{O_4}^{2 - } \\
2KOH \to 2{K^ + } + 2O{H^ - } The proton and hydroxide ion combine to form water. Since one sulphuric acid gives two protons, two KOH molecules are required to neutralise one sulphuric acid molecule. Potassium ion and sulphate ion combine to form potassium sulphate salt. $ 2{H^ + } + 2O{H^ - } \to 2{H_2}O \\\ 2{K^ + } + S{O_4}^{2 - } \to {K_2}S{O_4} $ In brief, the overall reaction can be written as, {H_2}S{O_4} + KOH \to {H_2}O + {K_2}S{O_4}$$

Note: HCl acts as acid and NaOH acts as base when the solvent is water. Similarly, $N{H_4}Cl$ acts as acid and $KN{H_2}$ act as base when solvent is taken as ammonia. In that case, the reaction of $N{H_4}Cl$ with $KN{H_2}$ is also a neutralisation reaction and the product of that reaction will be ammonia and the corresponding salt, KCl. Therefore it is not necessary that all neutralisation reactions should give water as one of the products. It depends on which solvent the reactants act as acid base.