Equilibrium - Ionic Equilibrium (Acids, Bases, and Salts)

Electrolytes: Substances that dissociate into ions in aqueous solution. Strong Electrolytes (e.g., $HCl$, $NaOH$, $NaCl$) dissociate completely, while Weak Electrolytes (e.g., $CH_3COOH$, $NH_4OH$) dissociate partially.

Arrhenius Theory: Acids produce $H^+$ ions in water; Bases produce $OH^-$ ions in water.

Brønsted-Lowry Theory: Acids are proton ($H^+$) donors; Bases are proton acceptors. This leads to the concept of Conjugate Acid-Base Pairs.

Lewis Theory: Acids are electron pair acceptors; Bases are electron pair donors.

Ostwald's Dilution Law: For a weak electrolyte with degree of dissociation $\alpha$, $K = \frac{C\alpha^2}{1-\alpha}$. For very weak electrolytes, $\alpha = \sqrt{\frac{K}{C}}$.

Ionic Product of Water ($K_w$): The product of molar concentrations of hydrogen and hydroxyl ions. At $298 \text{ K}$, $K_w = [H^+][OH^-] = 1.0 \times 10^{-14} \text{ mol}^2\text{L}^{-2}$.

pH Scale: Defined as the negative logarithm of the hydronium ion concentration: $pH = -\log_{10}[H_3O^+]$.

Common Ion Effect: The suppression of the degree of dissociation of a weak electrolyte by the addition of a strong electrolyte containing a common ion (e.g., adding $CH_3COONa$ to $CH_3COOH$).

Buffer Solutions: Solutions that resist changes in $pH$ upon addition of small amounts of acid or base. Acidic buffer: Weak acid + its salt with a strong base. Basic buffer: Weak base + its salt with a strong acid.

Solubility Product ($K_{sp}$): For a sparingly soluble salt $A_xB_y$, the equilibrium is $A_xB_y(s) \rightleftharpoons xA^{y+}(aq) + yB^{x-}(aq)$. The $K_{sp} = [A^{y+}]^x [B^{x-}]^y$ at saturation.

Salt Hydrolysis: The reaction of cations or anions of a salt with water to produce acidity or alkalinity. Salts of strong acids and strong bases do not undergo hydrolysis.