Question

Which one of the following is a strong electrolyte?

• A. Carbon disulfide
• B. Ammonium hydroxide
• C. Sodium chloride
• D. Water

Answer 1

The correct option is C

Sodium chloride

The explanation for the correct option (C):

• Strong electrolytes are those which completely ionize in an aqueous solution.
• For example, $\mathrm{HCl}$ is a strong electrolyte as it completely ionizes in the solution to produce Hydrogen ion (${\mathrm{H}}^{+}$) and Chloride ion (${\mathrm{Cl}}^{-}$).

$\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$

• Generally, strong acids and strong bases are considered strong electrolytes.
• Sodium chloride ($\mathrm{NaCl}$) is a salt that is formed from a strong acid, $\mathrm{HCl}$ and strong base, Sodium hydroxide ($\mathrm{NaOH}$). Since $\mathrm{NaCl}$ completely ionizes into Sodium ion (${\mathrm{Na}}^{+}$) and ${\mathrm{Cl}}^{-}$ ion in solution, it is considered a strong electrolyte.

$\mathrm{NaCl}\left(\mathrm{aq}\right)\to {\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$

The explanation for the incorrect options:

(A)

• Molecular compounds are those in which the bonds are formed by sharing of electrons between atoms, generally nonmetals.
• For example, Nitrogen dioxide (${\mathrm{NO}}_2$) is a molecular compound formed by sharing of electrons between Nitrogen $\left(\mathrm{N}\right)$ and Oxygen $\left(\mathrm{O}\right)$, where both $\mathrm{N}$ and $\mathrm{O}$ are nonmetals.
• Carbon disulfide (${\mathrm{CS}}_2$) consists of a Carbon ($\mathrm{C}$) and Sulfur ($\mathrm{S}$) atom.
• Both Carbon and Sulfur are nonmetals and they form ${\mathrm{CS}}_2$ by sharing electrons. Hence, ${\mathrm{CS}}_2$ is a molecular compound.
• Molecular compounds are generally weak or nonelectrolytes.

(B)

• Ammonium hydroxide (${\mathrm{NH}}_4\mathrm{OH}$) is a weak electrolyte as it ionizes partially in the solution to produce Ammonium ions (${\mathrm{NH}}_4^{+}$) and Hydroxide ions (${\mathrm{OH}}^{-}$).
• ${\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{aq}\right)\rightleftharpoons {\mathrm{NH}}_4^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$

(D)

• Water (${\mathrm{H}}_2\mathrm{O}$) ionizes partially into positively charged ${\mathrm{H}}^{+}$ ions and negatively charged ${\mathrm{OH}}^{-}$ ions. Hence, it is a weak electrolyte.
• ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$

Final Answer: Hence, option (C) is correct. Sodium chloride is a strong electrolyte.