H⁺
OH⁻
Acids & Bases
World B — Acids, Bases & Solutions
15.A — DEFINING ACIDS & BASES
HCl
H⁺
Cl⁻
R15.01 Arrhenius Concept
- Acids yield H⁺ in aqueous solution.
- Bases yield OH⁻ in aqueous solution.
- Limited strictly to water as a solvent.
HA
B
R15.02 Brønsted-Lowry Theory
- Acid = Proton (H⁺) donor.
- Base = Proton (H⁺) acceptor.
- Creates conjugate acid-base pairs.
B
A
R15.03 Lewis Theory
- Base = Electron-pair donor.
- Acid = Electron-pair acceptor.
- Most general definition, covers species without H.
← H⁺
H₂O
H⁺ →
R15.04 Amphoteric Substances
- Can act as either an acid or a base.
- Water (H₂O) can donate or accept a proton.
- Certain metal oxides (Al₂O₃, ZnO).
15.B — STRENGTH & CONCENTRATION
R15.05 Strong vs Weak Acids
- Strong: Complete dissociation in water (HCl).
- Weak: Partial dissociation (CH₃COOH).
- Strength ≠ Concentration.
R15.06 Strong vs Weak Bases
- Strong: Complete ionization (NaOH).
- Weak: Partial ionization (NH₃).
- Yields OH⁻ ions in solution.
R15.07 Concentrated vs Dilute
- Ratio of solute (acid/base) to solvent (water).
- Dilution: Adding water to a concentrated solution.
- Highly exothermic process (always add acid to water).
R15.08 Basicity & Acidity
- Basicity of Acid: Replaceable H⁺ ions (Monobasic, Dibasic).
- Acidity of Base: Replaceable OH⁻ ions (Monoacidic, Diacidic).
15.C — PROPERTIES & REACTIONS
vs
R15.09 Physical Properties
- Acids: Sour taste, turn blue litmus red.
- Bases: Bitter taste, soapy/slippery feel, turn red litmus blue.
- Both are corrosive.
R15.10 Reaction with Metals
- Acid + Metal → Salt + Hydrogen gas.
- H₂ burns with a 'pop' sound.
- Base + Metal → Salt + H₂ (Only specific metals like Zn, Al).
CO₂
CO₂
R15.11 Reaction with Carbonates
- Acid + Metal Carbonate → Salt + Water + CO₂.
- Brisk effervescence of carbon dioxide.
- CO₂ turns limewater milky.
H⁺
+OH⁻
→SALT
+H₂O
R15.12 Neutralisation
- Acid + Base → Salt + Water.
- Exothermic reaction (releases heat).
- H⁺ and OH⁻ combine to form H₂O.