Ionic Equilibrium

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According to Arrhenius concept, an acid is a substance that dissociates to give hydrogen ions (H⁺ or H₃O⁺) in aqueous solution. Example: HCl(g) + H₂O(l) → H₃O⁺(aq) + Cl⁻(aq). Limitation: Does not expl…

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Lowry-Bronsted theory defines: Acid = proton (H⁺) donor; Base = proton acceptor. Example: HCl + H₂O ⇌ H₃O⁺ + Cl⁻. Here HCl is acid (donates H⁺), H₂O is base (accepts H⁺). Advantage: Explains basic beh…

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Lewis acid = electron pair acceptor; Lewis base = electron pair donor. In BF₃ + NH₃ → F₃B-NH₃: BF₃ is Lewis acid (has vacant 2p orbital, accepts electron pair), NH₃ is Lewis base (has lone pair on N, …

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Kw is the ionic product of water: Kw = [H₃O⁺][OH⁻]. Derivation: Pure water: H₂O ⇌ H₃O⁺ + OH⁻. Experimentally at 25°C, [H₃O⁺] = [OH⁻] = 1×10⁻⁷ M. Therefore: Kw = (1×10⁻⁷)(1×10⁻⁷) = 1×10⁻¹⁴. This is con…

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Using Kw = [H₃O⁺][OH⁻]. Step 1: [OH⁻] = Kw/[H₃O⁺] = (1×10⁻¹⁴)/(2×10⁻³) = 5×10⁻¹² M. Step 2: Compare: [H₃O⁺] = 2×10⁻³ >> [OH⁻] = 5×10⁻¹² M. Conclusion: Solution is ACIDIC because [H₃O⁺] > [OH⁻] (and > …

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pH is defined as: pH = -log₁₀[H₃O⁺]. It measures hydrogen ion concentration on logarithmic scale. Calculation: HCl is strong acid, completely dissociates. [H₃O⁺] = 0.001 M = 10⁻³ M. pH = -log(10⁻³) = …

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When acid concentration is very low (< 10⁻⁶ M), [H₃O⁺] from water ionization (10⁻⁷ M) becomes significant. Total [H₃O⁺] = 10⁻⁷ (from HCl) + 10⁻⁷ (from water) = 2×10⁻⁷ M. pH = -log(2×10⁻⁷) = 7 - log(2)…

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Starting with: pH = -log[H₃O⁺] and pOH = -log[OH⁻]. Adding both: pH + pOH = -log[H₃O⁺] - log[OH⁻] = -log([H₃O⁺][OH⁻]) = -log(Kw). At 25°C, Kw = 10⁻¹⁴, so: pH + pOH = -log(10⁻¹⁴) = 14. This relationshi…