Question

For \[HCl,C{H_3}COOH,HN{O_2},N{H_3},KOH{\text{ and pyridine}}{\text{.}}\] Write as many salts formula. For each salt, write a chemical equation when salt is dissolved in water. Is the solution acidic basic or neutral?

Answer 1

Hint: Salts are ionic compounds formed from the neutralization reaction that takes place between acids and bases. The nature of salt depends completely on the relative strengths of the acids and bases being involved in the neutralization process.

Complete answer:
Ionic salts are the result of a neutralization reaction between an acid and a base. An aqueous solution of acids and bases behaves as electrolytes that dissociate to give their ions. The anionic part combines with the cationic part of the base to produce a salt and the hydroxide ions and hydrogen ions combine to form water.
\[HA(aq) \to {H^ + } + {A^ - }\]
\[BOH(aq) \to {B^ + } + O{H^ - }\]
\[HA + BOH \to AB + {H_2}O\]
Hydrochloric acid. Acetic acid and nitrous acid combine individually with bases like ammonia, pyridine and potassium hydroxide. The different salt formulas can be written by forming bonds with different pairs of anions and cations.
On dissolving these salts in water, the salts undergo hydrolysis and dissociate into ions which indicates their parent acids and bases. The salts can be categorized as acidic, basic or neutral depending on the type and strength of acid or base used. Strong acid-base reaction gives neutral salt, strong acid-weak base reaction gives acidic salt and strong base-weak acid reaction gives basic salt.
\[ \Rightarrow \] The salts can be written as follows:
A.\[N{H_4}Cl\] : acidic as formed from hydrochloric acid (strong acid) and ammonia (weak base)
\[N{H_4}Cl(aq) \to N{H_4}^ + + C{l^ - }\]
B.\[C{H_3}COON{H_4}\] : neutral as formed from weak acid and weak base i.e. acetic acid and ammonia
\[C{H_3}COON{H_4}(aq) \to N{H_4}^ + + C{H_3}CO{O^ - }\]
C.\[N{H_4}N{O_2}\] : acidic as formed from nitrous acid (strong acid) and ammonia (weak base)
\[N{H_4}N{O_2}(aq) \to N{H_4}^ + + N{O_2}^ - \]
D.\[KCl\] : neutral as formed from hydrochloric acid (strong acid) and potassium hydroxide (strong base)
\[KCl(aq) \to {K^ + } + C{l^ - }\]
E.\[C{H_3}COOK\] : basic as formed from acetic acid (weak acid) and potassium hydroxide (strong base)
\[C{H_3}COOK(aq) \to {K^ + } + C{H_3}CO{O^ - }\]
F.\[KN{O_2}\] : basic as formed from potassium hydroxide (strong base) and nitrous acid which is weak compared to the base.
\[KN{O_2}(aq) \to {K^ + } + N{O_2}^ - \]
G.\[pyridiniumCl\] : acidic as formed from hydrochloric acid (strong acid) and pyridine (very weak base)
\[pyridiniumCl(aq) \to pyridinium + C{l^ - }\]
H.\[pyridiniumN{O_2}\] : acidic as formed from nitrous acid (strong acid) and pyridine (very weak base)
\[pyridiniumN{O_2}(aq) \to pyridinium + N{O_2}^ - \]
I.\[pyridiniumC{H_3}COO\] : acidic as formed from acetic acid and pyridine is weak as compared to acid.
\[pyridiniumC{H_3}COO(aq) \to pyridinium + C{H_3}CO{O^ - }\]

Note:
The relative strength of an acid base when both of them are weak is decided by the value of their dissociation constant. If the dissociation constant of acid is greater than that of base then the acid is stronger as compared to base and an acidic salt is formed.