Answer:
a. the solution will be weakly basic.
b. Greater than 7 because CN⁻ is a stronger base than NH₄⁺ is an acid.
Explanation:
a. The fluoride ion (F⁻) reacts with water thus:
F⁻ + H₂O → HF + OH⁻
That means that fluoride ions produce OH⁻ ions in solution doing the solution will be weakly basic.
b. The acidic equilibrium of NH₄⁺ is:
NH₄⁺ ⇄ NH₃ + H⁺ with a ka of 5,6x10⁻¹⁰.
The basic equilibrium of CN⁻ is:
CN⁻ + H₂O → HCN + OH⁻ with a kb of 2x10⁻⁵
That means that the production of OH⁻ from CN⁻ is higher than production of H⁺ from NH₄⁺. The CN⁻ is a stronger base than NH₄⁺ is an acid.
Thus, the pH of a salt solution of NH₄CN would be Greater than 7 because CN⁻ is a stronger base than NH₄⁺ is an acid.
I hope ot helps!
