Question

Which one of the following is an acidic salt?

• A. $\mathrm{NaCl}$
• B. ${\mathrm{NH}}_4\mathrm{Cl}$
• C. ${\mathrm{NaHCO}}_3$
• D. ${\mathrm{Na}}_2{\mathrm{CO}}_3$

Answer 1

The correct option is B

${\mathrm{NH}}_4\mathrm{Cl}$

An explanation for the correct option

(B) ${\mathrm{NH}}_4\mathrm{Cl}$

Acids

• Acids, according to Arrhenius's theory, are species that dissociate in water to produce hydrogen ions ${\mathrm{H}}^{+}$.
• According to Brönsted-Lowry theory, an acid is a substance that can donate a hydrogen ion, ${\mathrm{H}}^{+}$.
• Consider the dissolution of ammonia $\left({\mathrm{NH}}_3\right)$ in water $\left({\mathrm{H}}_2\mathrm{O}\right)$, which is described by the following equation:

• According to Lewis's acid-base concept, acid is a species that accepts an electron pair.
• Lewis acids can be electron-deficient entities such as ${\mathrm{AlCl}}_3,{\mathrm{Co}}^{3+}$, and ${\mathrm{Mg}}^{2+}$.
• It has also been proven that strong acids have weak conjugate bases and vice versa.
• A strong base has a weak conjugate acid and vice versa.

${\mathrm{NH}}_4\mathrm{Cl}$

• An acidic salt is ammonium chloride $\left({\mathrm{NH}}_4\mathrm{Cl}\right)$.
• It's a salt of a strong acid, hydrochloric acid $\left(\mathrm{HCl}\right)$, and a weak base, ammonium hydroxide $\left({\mathrm{NH}}_4\mathrm{OH}\right)$.

An explanation for incorrect options

(A) $\mathbf{NaCl}$

• Sodium chloride $\left(\mathrm{NaCl}\right)$ is a neutral salt.

(C) ${\mathbf{NaHCO}}_{\mathbf{3}}$

• Sodium bicarbonate $\left({\mathrm{NaHCO}}_3\right)$ is a basic salt.

(D) ${\mathbf{Na}}_{\mathbf{2}}{\mathbf{CO}}_{\mathbf{3}}$

• Sodium carbonate $\left({\mathrm{Na}}_2{\mathrm{CO}}_3\right)$ is a basic salt.

Therefore, the correct option is (B) ${\mathbf{NH}}_{\mathbf{4}}\mathbf{Cl}$.