Final answer:
FeCl₃ (iron(III) chloride) forms an acidic solution when dissolved in water because its highly charged metal cation can hydrolyze, releasing H+ ions and lowering the pH.Option C is the correct answer.
Step-by-step explanation:
To determine which ionic compound forms an acidic solution when dissolved in water, we must consider the acid-base properties of the ions involved. A salt that derives from a strong acid and a strong base, like NaCl, will form a neutral solution, as neither ion will hydrolyze (react with water). However, if the cation is the conjugate acid of a weak base or a highly charged metal cation, it will tend to produce an acidic solution by reacting with the water to release H+ ions.
In the case of the options provided:
- NaHCO₃ (sodium bicarbonate) can act as a buffer due to its weakly basic nature; hence, its solution is slightly basic.
- KCl (potassium chloride) will form a neutral solution, as it comes from the neutralization of HCl by KOH.
- FeCl₃ (iron(III) chloride) has a highly charged metal cation, Fe³⁺, that can hydrolyze to produce an acidic solution.
- NaNO₃ (sodium nitrate) results from the neutralization of nitric acid by sodium hydroxide and forms a neutral solution.
Therefore, out of the compounds listed, FeCl₃ forms an acidic solution when dissolved in water.