Chapter 15 Summary: Formation Constant and Multiple Equilibria

Formation Constant (Kf)

• Equilibrium constant for the formation of a complex ion (Lewis acid + Lewis base -> adduct).

• Larger Kf = more stable ion.

• $Kf = \frac{[Products]}{[Reactants]}$

• Values are generally large.

Kf Calculation Example

• Set up an ICE table to solve for equilibrium concentrations.

• Account for coefficients.

Multiple Equilibria

• Occurs when more than one equilibrium reaction happens simultaneously.

Ocean Acidification Example

• Gaseous $CO<em>2$ forms aqueous $CO</em>2$ in the ocean.

• Aqueous $CO<em>2$ forms carbonic acid ($H</em>2CO_3$).

• Carbonic acid dissociates into proton and bicarbonate.

• Bicarbonate dissociates into carbonate and another proton.

• Increased acidity affects calcium carbonate concentrations, harming reefs.

Tooth Enamel and Acidity

• Bacteria in teeth produce acid, which can lead to cavities by consuming $OH$ and shifting the equilibrium to the right, which removes enamel.

• Fluoride in toothpaste converts hydroxylapatite to fluoroapatite, which is less soluble in acidic solutions.

Dissolution vs. Weak Electrolyte Formation

• Le Chatelier's principle applies when considering the effects of ions on slightly soluble solids in equilibrium.

Example Problem: Nickel(II) Carbonate in Water

• Write the equilibrium expression: $NiCO<em>3(s) \rightleftharpoons Ni^{2+}(aq) + CO</em>3^{2-}(aq)$

  • Adding nickel nitrate: shifts reaction left (less dissolves).

  • Adding potassium perchlorate: no effect (spectator ions).

  • Adding more nickel carbonate: no change (solid).

  • Adding potassium carbonate: shifts reaction left (less dissolves).

  • Adding nitric acid: shifts reaction right (more dissolves).

Key Takeaways

• Understand $K<em>{sp}$ and $K</em>f$.

• Know definitions of Lewis acids, Lewis bases, and Lewis acid-base adducts.