Question

Which of the following is a strong electrolyte?
A) $\text{ Ca(N}{\text{O}}_{\text{3}}{\text{)}}_{\text{2}}$
B) $\text{ HCN }$
C) ${\text{H}}_{\text{2}}\text{S}{\text{O}}_{\text{3}}$
D) $\text{ N}{\text{H}}_{\text{4}}\text{OH }$

Answer 1

Hint: The strong electrolytes are the solute which undergoes the complete ionization. Most of the inorganic salts are strong electrolytes in nature. However, the weak electrolytes are the solute which undergoes the partial dissociation.

Complete Solution :
A strong electrolyte is a solute that undergoes the complete or almost complete ionization of dissociation. A strong electrolyte is defined as the chemicals that dissociate completely into its ions.
A) Here calcium nitrate $\text{ Ca(N}{\text{O}}_{\text{3}}{\text{)}}_{\text{2}}$ undergoes complete ionization. It dissociates into calcium ion $\text{ C}{\text{a}}^{\text{2+ }}$ and nitrate ion ${\text{ NO}}_3^{-}$ in an aqueous solution. The ionization of calcium nitrate is as shown below,
$\text{ Ca(N}{\text{O}}_{\text{3}}{\text{)}}_{\text{2}}\to \text{ C}{\text{a}}^{\text{2+}}{\text{ + NO}}_3^{-}$

B) Hydrogen cyanide $\text{ HCN }$ is a weak acid. The ${\text{K}}_{\text{a }}$ value of the hydrogen cyanide is equal to $\text{ 6}\text{.2}\times \text{1}{\text{0}}^{-10}$ . It has a very small dissociation constant. It does not undergo $\text{ 100}{}^0/{}_0$ dissociation. It dissociates into the hydrogen ion and cyanide ion to a lesser extent. The dissociation of hydrogen cyanide is as shown below:
$\text{ HCN }\rightleftharpoons {\text{H}}^{\text{+}}\text{ + C}{\text{N}}^{-}$

C) Unlike ${\text{H}}_{\text{2}}\text{S}{\text{O}}_{\text{4 }}$ , the sulphurous acid ${\text{H}}_{\text{2}}\text{S}{\text{O}}_{\text{3}}$ is a weak acid. In an aqueous solution it does not undergo the complete dissociation to produce hydrogen ion or hydronium ion $\left({\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right)$ and bisulfite ion . The bisulphite is a strong base and readily abstracts a proton which reduces the degree of dissociation of sulphurous acid.

D) Ammonium hydroxide $\text{ N}{\text{H}}_{\text{4}}\text{OH }$ is a weak base.it ionizes to a lesser extent in an aqueous solution. The ammonium hydroxide dissociates to generate a hydroxide ion which recombines with the ammonium ion to produce ammonium hydroxide.
$\text{ N}{\text{H}}_{\text{4}}\text{OH }\rightleftharpoons {\text{ NH}}_4^{+}\text{ + O}{\text{H}}^{-}$
It does not undergo $\text{ 100}{}^0/{}_0$ dissociation. Thus ammonium hydroxide is a weak electrolyte.
Therefore, calcium nitrate $\text{ Ca(N}{\text{O}}_{\text{3}}{\text{)}}_{\text{2}}$ is a strong electrolyte but $\text{ N}{\text{H}}_{\text{4}}\text{OH }$, $\text{ HCN }$and ${\text{H}}_{\text{2}}\text{S}{\text{O}}_{\text{3}}$ are weak electrolytes.
So, the correct answer is “Option A”.

Note: Note that, strong acid, strong base, and their salts are strong electrolytes. When dissolved in water they produce ${\text{H}}^{\text{+ }}$ and $\text{O}{\text{H}}^{-}$ ions respectively. However, weak acid like $\text{ HF }$ , $\text{ C}{\text{H}}_{\text{3}}\text{COOH }$ , etc. and weak base like $\text{ N}{\text{H}}_{\text{3}}$ , ${\text{C}}_{\text{5}}{\text{H}}_{\text{5}}\text{N }$ , etc. are weak electrolytes.