‘Consider the acid-base nature of sodium fluoride, NaF, when it is dissolved in water What are the acid-base properties of the cation? (2) What are the acid-base properties of the anion? (3) Would an aqueous solution of sodium fluoride be acidic, basic Or neutral
The Correct Answer and Explanation is:
Correct Answer:
1) Acid-base properties of the cation (Na⁺):
The sodium ion (Na⁺) is the cation from sodium fluoride. Sodium comes from a strong base, sodium hydroxide (NaOH). Cations from strong bases do not hydrolyze in water and are considered neutral. Therefore, Na⁺ is neutral and has no significant acid-base properties in aqueous solution.
2) Acid-base properties of the anion (F⁻):
The fluoride ion (F⁻) is the conjugate base of the weak acid hydrofluoric acid (HF). In water, F⁻ can accept protons from water molecules, acting as a weak base. The reaction is:
F⁻ + H₂O ⇌ HF + OH⁻
This process produces hydroxide ions (OH⁻), which makes the solution basic.
3) Nature of aqueous solution of sodium fluoride:
Since the cation (Na⁺) is neutral and the anion (F⁻) is basic, the solution will be basic overall.
Explanation:
When sodium fluoride (NaF) dissolves in water, it breaks apart into sodium ions (Na⁺) and fluoride ions (F⁻). To predict whether the resulting solution will be acidic, basic or neutral, we must analyze both ions.
The sodium ion (Na⁺) is the product of a strong base, sodium hydroxide (NaOH). Cations from strong bases, such as Na⁺, do not interact with water in a way that affects pH. They are considered neutral because they do not donate protons or accept protons in water. Therefore, Na⁺ contributes no acidity or basicity to the solution.
The fluoride ion (F⁻), however, behaves differently. It is the conjugate base of hydrofluoric acid (HF), which is a weak acid. Conjugate bases of weak acids tend to hydrolyze in water. This means the fluoride ion reacts with water molecules to form hydroxide ions (OH⁻) and hydrofluoric acid (HF). The increase in hydroxide ions raises the pH, making the solution basic.
The chemical reaction is as follows:
F⁻ + H₂O ⇌ HF + OH⁻
Because hydroxide ions are produced in this equilibrium, the concentration of OH⁻ increases in the solution, resulting in a basic environment.
In summary, sodium fluoride dissolves to give a neutral cation and a weakly basic anion. The weak base reacts with water, producing hydroxide ions, so the final solution is basic.
