Q.Classify each of the following as a strong or a weak electrolyte and justify your classification in terms of the extent of ionization in aqueous solution: $\text{NaCl}$, $\text{CH}_3\text{COOH}$, $\text{HCl}$, $\text{NH}_4\text{OH}$.

[!TLDR] Strong electrolytes ionize essentially completely; weak electrolytes ionize only partially, in a genuine equilibrium. [!ANSWER] $\text{NaCl}$ and $\text{HCl}$ are strong electrolytes (essentially 100% ionized in solution); $\text{CH}_3\text{COOH}$ and $\text{NH}_4\text{OH}$ are we …

$\text{NaCl}$ is an ionic salt that dissociates completely on dissolving, $\text{NaCl}(s) \to \text{Na}^+(aq) + \text{Cl}^-(aq)$, with no meaningful reverse reaction — a strong electrolyte. $\text{HCl}$ is a strong acid that ionizes essentially completely in water, $\text{HCl} \to \text{H}^+ + \text{Cl}^-$ — also a strong electrolyte. By contrast, $\text{CH}_3\text{COOH}$ (acetic acid) ionizes only to a small extent, $\text{CH}_3\text{COOH} \rightleftharpoons \text{CH}_3\text{COO}^- + \text{H}^+$, with the majority of the acid remaining un-ionized at equilibrium — a weak electrolyte. Likewise $\text{NH}_4\text{OH}$ …

Judge each substance by whether it ionizes essentially completely (strong, single arrow) or only partially, in …

Do not confuse "strong electrolyte" with "concentrated solution" — the classification depends on the fraction ionized, which is a pr …