Question

Classify the following substances into strong electrolytes, weak electrolytes and non electrolytes. (a) acetic acid (b) ammonium sulphate. (c) ammonium hydroxide (d) carbon tetrachloride (e) sodium acetate (f) dilute hydrochloric acid (g) dilute sulphuric acid.

Answer 1

Strong electrolytes are those which dissociates completely in aqueous solution.

Weak electrolytes are those which dissociates to small extent in aqueous solution.

Non-electrolytes are those which do not dissociates into ions in aqueous or molten state.

From the given substances :

(a) Acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$, (c) Ammonium hydroxide $\left({\mathrm{NH}}_4\mathrm{OH}\right)$ are weak electrolytes.

$$\begin{gathered} {\mathrm{CH}}_3\mathrm{COOH}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{H}}_3{\mathrm{O}}^{+}+{\mathrm{CH}}_3{\mathrm{COO}}^{-} \\ \mathrm{acetic}\mathrm{acid}\mathrm{hydronium}\mathrm{ion}\mathrm{acetate}\mathrm{ion} \end{gathered}$$

$$\begin{gathered} {\mathrm{NH}}_4\mathrm{OH}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{NH}}_4^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right) \\ (\mathrm{ammonium}\mathrm{ammonium}\mathrm{ion}\mathrm{hydronium}\mathrm{ion} \\ \mathrm{hydroxide}) \end{gathered}$$

(f) dilute hydrochloric acid $\left(\mathrm{HCL}\right)$, (g) dilute sulphuric acid $\left(\mathrm{H}2{\mathrm{SO}}_4\right)$, (b) ammonium sulphate $\left[{\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4\right]$, (e) sodium acetate $\left({\mathrm{CH}}_3\mathrm{COONa}\right)$ are strong electrolytes.

$$\begin{gathered} \mathrm{dil}.\mathrm{HCl}\stackrel{{\mathrm{H}}_2\mathrm{O}}{\rightleftharpoons }{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right) \\ \mathrm{hydrochloric}\mathrm{hydronium}\mathrm{ion}\mathrm{chlorine}\mathrm{ion} \\ \mathrm{acid} \end{gathered}$$

$$\begin{gathered} \mathrm{dil}.{\mathrm{H}}_2{\mathrm{SO}}_4\stackrel{{\mathrm{H}}_2\mathrm{O}}{\rightleftharpoons }{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)+{{\mathrm{HSO}}_4}^{-} \\ (\mathrm{sulphuric}\mathrm{acid})(\mathrm{hydronium}\mathrm{ion})(\mathrm{hydrogen}\mathrm{sulphate}\mathrm{ion}) \end{gathered}$$

$$\begin{gathered} {\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4\left(\mathrm{s}\right)\stackrel{2{\mathrm{H}}_2\mathrm{O}}{\rightleftharpoons }2{\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{aq}\right)+2{\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{SO}}_4^{2-}\left(\mathrm{aq}\right) \\ \mathrm{ammonium}\mathrm{ammonium}\mathrm{proton}\mathrm{sulphate}\mathrm{ion} \\ \mathrm{sulphate}\mathrm{hydroxide} \end{gathered}$$

$$\begin{gathered} {\mathrm{CH}}_3\mathrm{COONa}\stackrel{{\mathrm{H}}_2\mathrm{O}}{\rightleftharpoons }{\mathrm{CH}}_3{\mathrm{COO}}^{-}\left(\mathrm{aq}\right)+{\mathrm{Na}}^{+}\left(\mathrm{aq}\right) \\ (\mathrm{sodium}(\mathrm{acetate}\mathrm{ion})(\mathrm{sodium}\mathrm{ion}\left) \\ \mathrm{acetate}\right) \end{gathered}$$

(d) carbon tetrachloride $\left({\mathrm{CCl}}_4\right)$ is a non-electrolyte. ${\mathrm{CCl}}_4$ is a covalent compound which will not be dissociate on electrolysis.