Question

in the reaction of aqueous aluminum chloride with aqueous potassium hydroxide, _______ is formed as the precipitate: (see solubility rules).

1. potassium chloride
2. aluminum hydroxide
3. both aluminum hydroxide and potassium chloride
4. potassium hydroxide
5. no precipitates are formed.

Explanation:

1. First, write the chemical reaction: $\ce{AlCl_{3}(aq) + 3KOH(aq) -> Al(OH)_{3}(s) + 3KCl(aq)}$.
2. Then, apply solubility rules: Potassium chloride ($\ce{KCl}$) is soluble (group 1 metal salts are soluble). Aluminum hydroxide ($\ce{Al(OH)_{3}}$) is insoluble (hydroxides of most metals except group 1, $\ce{Ca^{2+}}$, $\ce{Sr^{2+}}$, $\ce{Ba^{2+}}$ are insoluble). So $\ce{Al(OH)_{3}}$ precipitates, while $\ce{KCl}$ stays dissolved.

Answer:

1. Aluminum hydroxide