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Cheat sheet · Class 12 · CBSE · Science Chemistry

Solutions cheat sheet

The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.

CBSE Class 12 · Chemistry

Cheat sheet

Chapter 1Solutions

Colligative properties depend on the number of solute particles, not their nature.

1. Concentration

  • Molarity (mol/L), molality (mol/kg), mole fraction, ppm, mass %.
  • Henry's law: p=KHxp = K_Hx — gas solubility ∝ pressure.

2. Raoult's Law

pA=pA∘xAp_A = p_A^\circ x_A
p=pA∘xA+pB∘xBp = p_A^\circ x_A + p_B^\circ x_B
  • Ideal: obeys Raoult's law, ΔH_mix = 0, ΔV_mix = 0.
  • Positive deviation: weaker A–B forces (ethanol + acetone); minimum-boiling azeotrope.
  • Negative deviation: stronger A–B forces (chloroform + acetone); maximum-boiling azeotrope.

3. Colligative Properties

PropertyFormula
Relative lowering of vapour pressurep∘−pp∘=xB\dfrac{p^\circ - p}{p^\circ} = x_B
Elevation of boiling pointΔTb=Kbm\Delta T_b = K_bm
Depression of freezing pointΔTf=Kfm\Delta T_f = K_fm
Osmotic pressureπ=CRT\pi = CRT

van 't Hoff factor ii: multiply each formula by ii (e.g. NaCl, i ≈ 2; acetic acid in benzene, i ≈ 0.5).

4. Key Points

  • Isotonic solutions: equal π.
  • Reverse osmosis: desalination.
  • Molality is temperature-independent.
  • Abnormal molar mass from association/dissociation.

Remember: Raoult & deviations | 4 colligative formulas | van 't Hoff i

Solutions: questions and notes

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