Is the solubility of Zn(OH)₂ increased, decreased, or unchanged on addition of each of the following substances? Write a balanced net ionic equation for each dissolution reaction. (See Appendix C.6 for formulas of complex ions.) (b) KOH

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1. Identify the solubility equilibrium of Zn(OH)_2. The dissolution of Zn(OH)_2 in water can be represented by the equilibrium: Zn(OH)_2(s) ⇌ Zn^{2+}(aq) + 2OH^-(aq).
2. Consider the effect of adding KOH to the solution. KOH is a strong base that dissociates completely in water to give K^+ and OH^- ions.
3. Apply Le Chatelier's Principle to predict the shift in equilibrium. The addition of OH^- ions from KOH will increase the concentration of OH^- in the solution.
4. Determine the effect on solubility. According to Le Chatelier's Principle, the equilibrium will shift to the left to counteract the increase in OH^- concentration, thus decreasing the solubility of Zn(OH)_2.
5. Write the net ionic equation for the dissolution of Zn(OH)_2 in the presence of excess OH^-: Zn(OH)_2(s) + 2OH^-(aq) ⇌ Zn(OH)_4^{2-}(aq). This shows the formation of a complex ion, which can increase solubility if the complex ion is stable.