Question

which equation describes the dissociation of alcl₃ as it dissolves in water? alcl₃ → al³⁺ + 3cl⁻ alcl₃ → al³⁺ + cl₃⁻ 2alcl₃ → 2al + 3cl₂

Explanation:

To determine the correct dissociation equation for \( \text{AlCl}_3 \) in water, we analyze the ionic composition. Aluminum chloride (\( \text{AlCl}_3 \)) is an ionic compound that dissociates into its constituent ions. Aluminum has a \( +3 \) charge (\( \text{Al}^{3+} \)), and chlorine has a \( -1 \) charge (\( \text{Cl}^- \)). In \( \text{AlCl}_3 \), there is 1 \( \text{Al}^{3+} \) ion and 3 \( \text{Cl}^- \) ions (since the overall charge of the compound is neutral: \( +3 + 3(-1) = 0 \)).

• The first option: \( \text{AlCl}_3

ightarrow \text{Al}^{3+} + 3\text{Cl}^- \) correctly shows the dissociation into one \( \text{Al}^{3+} \) and three \( \text{Cl}^- \) ions.

• The second option: \( \text{AlCl}_3

ightarrow \text{Al}^{3+} + \text{Cl}_3^- \) is incorrect because \( \text{Cl}_3^- \) is not a valid ion; chlorine ions exist as \( \text{Cl}^- \), not a triatomic ion with a \( -1 \) charge.

• The third option: \( 2\text{AlCl}_3

ightarrow 2\text{Al} + 3\text{Cl}_2 \) represents a decomposition reaction (producing elemental aluminum and chlorine gas), not a dissociation into ions in water. Dissociation in water involves forming ions, not elemental substances.

So, the correct equation is the first one.

Answer:

A. \( \text{AlCl}_3
ightarrow \text{Al}^{3+} + 3\text{Cl}^- \)