Question

Classify each solute represented in the following equations as a strong, weak, or nonelectrolyte: a. \(\mathrm{CH}_{3} \mathrm{OH}(l) \stackrel{\mathrm{H}_{2} \mathrm{O}}{\longrightarrow} \mathrm{CH}_{3} \mathrm{OH}(a q)\) b. \(\mathrm{MgCl}_{2}(s) \stackrel{\mathrm{H}_{2} \mathrm{O}}{\longrightarrow} \mathrm{Mg}^{2+}(a q)+2 \mathrm{Cl}^{-}(a q)\) c. \(\mathrm{HClO}(a q) \stackrel{\mathrm{H}_{2} \mathrm{O}}{\stackrel{+}{\longrightarrow} \mathrm{H}^{+}(a q)+\mathrm{ClO}^{-}(a q)}\)

Short answer

a. Nonelectrolyte. b. Strong electrolyte. c. Weak electrolyte.

Step-by-step solution

- Identify the nature of the solute in part (a)

Look at the equation ewline \(\text{CH}_{3} \text{OH}(l) \stackrel{\text{H}_{2}\text{O}}{\longrightarrow} \text{CH}_{3} \text{OH}(aq)\)) Å The substance involved here is methanol, \(\text{CH}_{3} \text{OH}\). It does not dissociate into ions when dissolved in water and thus remains as \(\text{CH}_{3} \text{OH}(aq).\) Hence, it is a nonelectrolyte.

- Identify the nature of the solute in part (b)

Look at the equation ewline \( \text{MgCl}_{2}(s) \stackrel{\text{H}_{2} \text{O}}{\longrightarrow}\text{Mg}^{2+}(a \text{q} )+2\text{Cl}^{-}( \text{a q} )\). Here,\text{MgCl}_{2} dissociates completely into \text{Mg}^{2+} ions and \text{Cl}^{-} ions. This complete dissociation into ions in water classifies \(\text{MgCl}_{2}\) as a strong electrolyte.

- Identify the nature of the solute in part (c)

Look at the equation\( \text{HClO}( \text{a q} ) \stackrel{\text{H}_{2} \text{O}}{\rightarrow} \text{H}^{+}( \text{a q}) + \text{ClO}^{-}( \text{a q})\). \text{HClO} (hypochlorous acid) partially dissociates in water to produce \(\text{H}^{+}\) and \(\text{ClO}^{-}\) ions. Partial dissociation means \(\text{HClO}\) is classified as a weak electrolyte.

Key concepts

Strong Electrolytes

Strong electrolytes are substances that completely dissociate into ions when dissolved in water. This means they break apart fully into their respective ions.
When a strong electrolyte dissolves in water, it produces a solution that can conduct electricity very efficiently.
For example, in the equation:
\[\text{MgCl}_2(s) \rightarrow \text{Mg}^{2+}(aq) + 2\text{Cl}^-(aq)\], magnesium chloride (\text{MgCl}_2) dissociates completely into magnesium ions (\text{Mg}^{2+}) and chloride ions (\text{Cl}^-) in water.
This complete dissociation is why \text{MgCl}_2 is classified as a strong electrolyte.

Weak Electrolytes

Weak electrolytes do not completely dissociate into ions in water. Instead, they partially dissociate into ions.
As a result, the solution contains both dissociated ions and undissociated molecules. This partial dissociation means the solution can conduct electricity, but not as well as a strong electrolyte.
For example, hypochlorous acid (\text{HClO}) in the equation: \[\text{HClO}(aq) \rightarrow \text{H}^{+}(aq) + \text{ClO}^-(aq)\], partially dissociates into hydrogen ions (\text{H}^+) and hypochlorite ions (\text{ClO}^-).
Because of this partial dissociation, \text{HClO} is classified as a weak electrolyte.

Nonelectrolytes

Nonelectrolytes are substances that do not dissociate into ions at all when dissolved in water.
This means they remain entirely as molecules and do not produce ions in the solution.
Since they do not form ions, nonelectrolytes do not conduct electricity.
For example, methanol (\text{CH}_3\text{OH}) in the equation: \[\text{CH}_3\text{OH}(l) \rightarrow \text{CH}_3\text{OH}(aq)\], remains as \text{CH}_3\text{OH} when dissolved in water, not breaking down into ions at all.
Hence, methanol is considered a nonelectrolyte.

Dissociation

Dissociation is the process by which a compound separates into its ionic components when dissolved in water.
In this process, strong electrolytes completely dissociate and weak electrolytes partially dissociate.
For instance, \text{MgCl}_2 completely dissociates into \text{Mg}^{2+} and \text{Cl}^- ions: \[\text{MgCl}_2(s) \rightarrow \text{Mg}^{2+}(aq) + 2\text{Cl}^-(aq)\]
In contrast, \text{HClO} partially dissociates into \text{H}^+ and \text{ClO}^- ions: \[\text{HClO}(aq) \rightarrow \text{H}^{+}(aq) + \text{ClO}^-(aq)\].
Nonelectrolytes, such as \text{CH}_3\text{OH}, do not dissociate at all and remain as molecules.

Chemical Equations

Chemical equations represent the process of chemical reactions, showing how substances react to form products.
In the context of electrolytes, these equations illustrate how substances dissociate into ions.
For example, the equation: \[\text{MgCl}_2(s) \rightarrow \text{Mg}^{2+}(aq) + 2\text{Cl}^-(aq)\] shows the complete dissociation of \text{MgCl}_2.
Another example is: \[\text{HClO}(aq) \rightarrow \text{H}^{+}(aq) + \text{ClO}^-(aq)\], which shows the partial dissociation of \text{HClO} into its ions.
These equations help us classify substances as strong, weak, or nonelectrolytes based on their dissociation behavior.