Answer:
An aqueous solution of NaF will produce a neutral solution.
Explanation:
In order to classify the solutions, we need to dissociate all the salts and determine the conjugate pairs of base and acids.
NaNO₂ → Na⁺ + NO₂⁻
Na⁺ comes from the NaOH, a strong base, so the Na⁺ is the conjugate weak acid from the strong base. It will not react. This is a basic salt.
The NO₂⁻ is a conjugate strong base, that comes from the weak acid, nitrous acid. This ion can make hydrolisis.
NO₂⁻ + H₂O ⇄ HNO₂ + OH⁻ Kb
We give OH⁻ to medium, so solution is basic.
Li₂CO₃ → 2Li⁺ + CO₃⁻²
Li⁺ comes from the LiOH, a strong base, so the cathion is the conjugate weak acid from the strong base. It will not react
The CO₃⁻² is a conjugate strong base, that comes from the weak acid, carbonic acid. This ion can make hydrolisis.
CO₃⁻² + H₂O ⇄ HCO₃⁻ + OH⁻ Kb
NaClO₄ → Na⁺ + ClO₄⁻
Na⁺ comes from the NaOH, a strong base, so the cathion is the conjugate weak acid from the strong base. It will not react
The ClO₄⁻ is a conjugate strong base, that comes from the weak acid, perchloric acid. This ion can make hydrolisis. This is a basic salt.
ClO₄⁻ + H₂O ⇄ HClO₄⁻ + OH⁻ Kb
NH₄ClO₄ → NH₄⁺ + ClO₄⁻
Both ions can make hydrolisis. Ammonium comes from a weak base, so it is the strong conjugate base, and ClO₄⁻ is a conjugate strong base, that comes from the weak acid, perchloric acid
NH₄⁺ + H₂O ⇄ NH₃ + H₃O⁺ Ka
ClO₄⁻ + H₂O ⇄ HClO₄⁻ + OH⁻ Kb
This sort of salt are generally acid.
NaF → Na⁺ + F⁻
As we have seen, Na⁺ comes from the NaOH (a strong base) so it will not react.
This equilibrium can not occur: Na⁺ + H₂O ← NaOH + H⁺
F⁻ comes from a strong acid, HF so it will not also react. This reaction can not occur too: F⁻ + H₂O ← HF + OH⁻
We do not have reaction in this neutral salt, so the pH is neutral.
