Chemistry 112

First, dissociate the salt into ions:

ZnF2(aq) → Zn2+(aq) + 2 F(aq)

Check the cation for hydrolysis:

Zn2+(aq) + 2 H2O(l) ZnOH+(aq) + H3O+(aq)

Yes, the reaction does occur because ZnOH+ is a weak base.

Check the anion for hydrolysis:

F(aq) + H2O(l) HF(aq) + OH(aq)

This reaction does occur because HF is a weak acid.

Net: we need the equilibrium constants to decide (from the Table of Acid Ionization Constants).

Ka(Zn2+) = 2.5×10–10

Ka(HF) = 6.6×10–4

Kb (F) = 1.0×10–14/6.6×10–4 = 1.5×10–11

2.5×10–10 > 1.5×10–11

 

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