Question. which-one-of-the-following-is-not-a-strong-electrolyte in water: \(\mathrm{NaCl(aq)}\), \(\mathrm{HCl(aq)}\), \(\mathrm{NaOH(aq)}\), \(\mathrm{CH_3COOH(aq)}\), or \(\mathrm{CaCl_2(aq)}\)?
Key criterion for a strong electrolyte
A strong electrolyte produces ions essentially completely in aqueous solution. Typical strong electrolytes include:
- Soluble ionic salts (they dissociate into ions in water).
- Strong acids (they ionize essentially completely, producing \(\mathrm{H_3O^+}\)).
- Strong bases (they dissociate essentially completely, producing \(\mathrm{OH^-}\)).
A weak electrolyte ionizes only partially (typical of weak acids and weak bases), so it is not a strong electrolyte.
Classify each option
| Substance | Type in water | Representative equation | Electrolyte classification |
|---|---|---|---|
| \(\mathrm{NaCl(aq)}\) | Soluble ionic salt (dissociation) | \(\mathrm{NaCl \rightarrow Na^+ + Cl^-}\) | Strong electrolyte |
| \(\mathrm{HCl(aq)}\) | Strong acid (ionization) | \(\mathrm{HCl + H_2O \rightarrow H_3O^+ + Cl^-}\) | Strong electrolyte |
| \(\mathrm{NaOH(aq)}\) | Strong base (dissociation) | \(\mathrm{NaOH \rightarrow Na^+ + OH^-}\) | Strong electrolyte |
| \(\mathrm{CH_3COOH(aq)}\) | Weak acid (partial ionization) | \(\mathrm{CH_3COOH + H_2O \rightleftharpoons H_3O^+ + CH_3COO^-}\) | Not a strong electrolyte (weak electrolyte) |
| \(\mathrm{CaCl_2(aq)}\) | Soluble ionic salt (dissociation) | \(\mathrm{CaCl_2 \rightarrow Ca^{2+} + 2Cl^-}\) | Strong electrolyte |
Conclusion
The substance that is not a strong electrolyte is \(\mathrm{CH_3COOH(aq)}\). Acetic acid is a weak acid, so it ionizes only partially in water and produces relatively few ions compared with strong electrolytes.