Question

For each of the following compounds, decide whether the compound's solubility in aqueous solution changes with pH. If the solubility does change, pick the pH at which you'd expect the highest solubility.

highest solubility compound Does solubility change with pH? pH = 10 pH = 8 pH = 7 MgCl2 gyes O no 0 Zns O yes O no 0 O yes Ni(OH), no

Answer 1

a) MgCl₂ is salt of strong base and strong acid The dissociation is given below - Macl Mg2+ + 201 Bothions would not form base or acid in the given pH range as solubility does not Change with pH No effect of pH on solubility of MgCl₂ b) Zns is salt of weak acid and weak base zns dissociate as - ZnS - Zn2+ + 32 In basic medium conc. of of increwes with increase in pH and consumes more zn2tions results reaction shift in forward direction and solubility increase - Hence, solubility of ans is highest at pH=10 Solubility of base decreases with increase in pH as reaction shift in backword digreetion due increase in conc. of OH- I NICOLD = Ni 2+ + 204- Therefore, solubility of NICOH)2 is maximum at pH-7 Teacher's Signature