Colligative properties: relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, osmotic pressure
Solutions · Chemistry
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1 mol of NaCl in 1 kg water: find ΔT_f. (K_f water = 1.86 K·kg/mol) Step 1: NaCl dissociates: i ≈ 2 (Na⁺ + Cl⁻). Step 2: ΔT_f = i·K_f·m = 2 × 1.86 × 1 = 3.72 K. Step 3: Solution freezes at −3.72°C instead of 0°C. Step 4: Real i is slightly less than 2 (ion pairing) — measured ~3.4°C. This is why salt melts ice on roads.