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Solutions

NCERT Class 12 Chemistry Chapter 1

Solutions for Class 12 Chemistry, JEE and NEET: concentration, Henry’s and Raoult’s laws, ideal and non-ideal solutions and colligative properties.

7 topics Updated 8 Nov 2026

For: Class 12, JEE and NEET

In the syllabus: JEE Class 12 syllabus, NEET Class 12 syllabus

With your textbook

NCERT Chemistry Part I (Class 12), Chapter 1 “Solutions”, reprint 2026-27.

Open the official NCERT chapter (PDF, 3.9 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. Types of solutions

    Solvent and solute, binary solutions and the nine gaseous, liquid and solid types, with examples.

    NCERT Section 1.1 9 min read 4 solved examples 8 practice questions

  2. Expressing the concentration of solutions

    Mass, volume and w/V percentage, ppm, mole fraction, molarity, molality, conversions and examples.

    NCERT Section 1.2 14 min read 5 solved examples 9 practice questions

  3. Solubility and Henry’s law

    Like dissolves like, saturated solutions, effect of temperature and pressure, and Henry’s law, its formula and uses.

    NCERT Section 1.3 16 min read 5 solved examples 8 practice questions

  4. Vapour pressure of liquid solutions

    Vapour pressure of liquid solutions, the total pressure formula, vapour composition and non-volatile solutes.

    NCERT Section 1.4 15 min read 5 solved examples 8 practice questions

  5. Ideal and non-ideal solutions

    Raoult’s law, positive and negative deviations with graphs, causes, examples and azeotropes.

    NCERT Section 1.5 12 min read 4 solved examples 8 practice questions

  6. Colligative properties and determination of molar mass

    Vapour pressure lowering, ΔTb, ΔTf, Kb, Kf, osmosis, isotonic solutions, reverse osmosis, molar mass.

    NCERT Section 1.6 20 min read 7 solved examples 10 practice questions

  7. Abnormal molar masses and the van ’t Hoff factor

    Abnormal molar mass, modified colligative formulas, degree of association and dissociation, examples.

    NCERT Section 1.7 15 min read 5 solved examples 10 practice questions

Key formulas in this chapter

Types of solutions

  • Gaseous solutions: O in N; CHCl in N; camphor in N
  • Liquid solutions: O, CHOH or glucose in water
  • Solid solutions: H in Pd; Hg with Na; Cu in Au
  • Brass: Cu + Zn; bronze: Cu + Sn; German silver: Cu + Zn + Ni
  • ppm = (parts of component ÷ total parts) × 10

Concentration of solutions

  • Mass % = (mass of component ÷ mass of solution) × 100
  • Volume % = (volume of component ÷ volume of solution) × 100
  • ppm = (parts of component ÷ total parts) × 10
  • xA = nA/(nA + nB); x1 + x2 + … = 1
  • M = moles of solute ÷ volume of solution in L
  • m = moles of solute ÷ mass of solvent in kg
  • m = 1000M/(1000d − M × MB), with d in g/mL and MB in g/mol
  • MV = MV (dilution)

Solubility

  • Solute + solvent ⇌ solution
  • p = KH x
  • x ≈ ngas/nwater (dilute)
  • Δsol H > 0: solubility rises with T; Δsol H < 0: it falls

Vapour pressure of solutions

  • p1 = x1 p1^0; p2 = x2 p2^0
  • ptotal = p1 + p2 = p1^0 + (p2^0 − p1^0) x2
  • pi = yi ptotal
  • Henry: p = KH x; for an ideal solution KH = pi^0
  • 1/ptotal = y1/p1^0 + y2/p2^0

Ideal and non-ideal solutions

  • Ideal: Δmix H = 0, Δmix V = 0, Δmix S > 0, Δmix G < 0
  • Positive deviation: p > p(Raoult); usually Δmix H > 0, Δmix V > 0
  • Negative deviation: p < p(Raoult); usually Δmix H < 0, Δmix V < 0

Colligative properties

  • (p1^0 − p1)/p1^0 = x2 ≈ (w2 M1)/(M2 w1)
  • ΔTb = Kb m
  • ΔTf = Kf m
  • m = 1000 w2/(M2 w1)
  • M2 = 1000 K w2/(ΔT w1), with Kb or Kf
  • Kf = R M1 Tf^2/(1000 Δfus H)
  • Π = CRT
  • M2 = w2 RT/(Π V)

Abnormal molar masses

  • i = normal molar mass ÷ abnormal molar mass
  • ΔTb = i Kb m
  • ΔTf = i Kf m
  • Π = i n2 RT/V
  • Dimerisation: i = 1 − x/2
  • Dissociation into ν particles: i = 1 + (ν − 1) x

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