1. Haber Process (Ammonia Synthesis)

$N_{2}$(g) + $3H_{2}$(g) --[Fe catalyst, 400-500°C, 150-200 atm]--> $2NH_{3}$(g) $\Delta H$ = −92 kJ/mol (exothermic)

• Le Chatelier optimisation: High pressure shifts toward fewer gas moles ($\Delta n$ = −2) → favours $NH_{3}$
• Temperature compromise: Low T favours $NH_{3}$ (exothermic) but reaction is too slow; 400–500°C used with catalyst
• Catalyst: Fe with $K_{2}O$ and $Al_{2}O_{3}$ promoters; does not change K but speeds equilibration

2. Blood Buffer System

• Blood pH = 7.35–7.45 (slightly basic)
• Carbonate buffer: $CO_{2}$/$HCO_{3}^{-}$ system; pKa ≈ 6.1
• Henderson-Hasselbalch: $pH = 6.1 + \log\frac{[\text{HCO}_3^-]}{[\text{CO}_2]}$ ≈ 6.1 + log(20/1) ≈ 7.4
• Acidosis: pH < 7.35; Alkalosis: pH > 7.45

3. Selective Precipitation in Qualitative Analysis

• Adding $H_{2}S$ in acidic medium selectively precipitates Group II cations (low Ksp sulfides)
• Adding $H_{2}S$ in basic medium precipitates Group III cations (higher Ksp sulfides)
• Exploits Ksp differences and common ion effect ($H^{+}$ concentration controls $S^{2-}$ concentration)

4. Antacids

• Mg(OH){2} and Al(OH){3} in antacids neutralise excess HCl in stomach (Arrhenius base concept)
• Mg(OH)_{2} + 2HCl → $MgCl_{2}$ + $2H_{2}O$
• Calcium carbonate (SMILES: OC(=O)[O-].[Ca+2]): $CaCO_{3}$ + 2HCl → $CaCl_{2}$ + $H_{2}O$ + $CO_{2}$

5. Solubility in Water Treatment

• Lime softening: $Ca^{2+}$ + $CO_{3}^{2-}$ → $CaCO_{3}$↓ (ionic product exceeds Ksp)
• Fluoridation controlled by $CaF_{2}$ Ksp to maintain safe [$F^{-}$] levels