Answer:
a. pH > 7 ; b. pH > 7 ; c. pH = 7 ; d. pH = 7 ; e. pH < 7 ; f. pH < 7
Explanation:
a. NH₄Br → NH₄⁺ + Br⁻
The ammonium is the conjugate strong acid from a weak base, so it will react in water. Bromine, is the conjugate weak base from a strong acid and it does not react in water. As the NH₄⁺ react as this:
NH₄⁺ + H₂O ⇄ NH₃ + OH⁻ (pH > 7; brings hydroxyls to the medium)
b. Na₂CO₃ → 2Na⁺ + CO₃⁻²
The sodium cation is the conjugate weak acid from a strong base, in water in does not react. The carbonate is the conjugate strong base from a weak acid, so it can react in water as this:
CO₃⁻² + H₂O ⇄ HCO₃⁻ + OH⁻
HCO₃⁻ + H₂O ⇄ H₂CO₃ + OH⁻ (pH > 7; brings hydroxyls to the medium)
c. KF → K⁺ + F⁻
Both ions come from a base and a strong acid, so they will be the weak conjugate base and acid. They will not have a reaction in the water, so the solution will be neutral
d. KBr → K⁺ + Br⁻ (same as before)
e. AlCl₃ → Al³⁺ + 3Cl⁻
Cl⁻ is a conjugate weak base, from a strong acid and it doesn't react in water. But the Al³⁺ which comes from the Al(OH)₃ is amphoteric, it can act as an acid or a base. In this case, you have a complex and the solution will be acid.
Al³⁺ + H₂O ⇄ Al(OH)²⁺ + H⁺ (it brings protons to the medium, pH < 7)
f. Cu(NO₃)₂ → Cu²⁺ + 2NO₃⁻
Ion Cu²⁺ comes from the Cu(OH)₂, a weak base so it is a conjugate strong acid. The nitrate, comes from a strong acid (nitric) , so it is the conjugate weak base of it, it won't react in water.
Cu²⁻ + H₂O ⇄ Cu(OH)⁺ + H⁺
You will have a complex, and you are bringing protons to the medium, so pH < 7
