Comprehensive notes on Acids and Bases, Bronsted-Lowry & Lewis Concepts, pH, pOH, Dissociation Constants (Ka, Kb), Common Ion Effect, Buffers, and Salt Hydrolysis.
Bronsted-Lowry Concept: Acid is a proton (H+) donor; Base is a proton acceptor. Conjugate Acid-Base Pair: Pair determining by loss/gain of a proton (e.g., HCl / Cl-).
Lewis Concept: Acid is an electron pair acceptor (e.g., BF3); Base is an electron pair donor (e.g., NH3).
Auto-ionization: H2O ↔ H+ + OH-.
Kw: [H+][OH-] = 1.0 x 10-14 at 25°C.
pH: -log[H+]. pOH: -log[OH-].
pH + pOH = 14.
Ka: Dissociation constant for weak acid. HA ↔ H+ + A-. Ka = [H+][A-]/[HA]. Larger Ka → Stronger Acid.
pKa: -log(Ka). Smaller pKa → Stronger Acid.
Kb: Dissociation constant for weak base.
The suppression of ionization of a weak electrolyte by adding a strong electrolyte containing a common ion. Application: Purification of NaCl, Salting out of soap.
Solutions which resist change in pH when small amounts of acid or base are added.
Acidic Buffer: Weak Acid + Salt with Strong Base (CH3COOH + CH3COONa). pH < 7.
Basic Buffer: Weak Base + Salt with Strong Acid (NH4OH + NH4Cl). pH > 7.
Henderson-Hasselbalch Eq: pH = pKa + log([Salt]/[Acid]).
Reaction of cation or anion of a salt with water to produce acidic or alkaline solution.
Acidic Salt: Strong Acid + Weak Base (NH4Cl → Acidic, pH < 7).
Basic Salt: Weak Acid + Strong Base (Na2CO3 → Basic, pH > 7).
Neutral Salt: Strong Acid + Strong Base (NaCl → Neutral, pH = 7).