Solutions & Colligative Properties Class 12 chemistry handwritten notes

📚 Class 12 🧪 Chemistry ✅ Chapter 2 📝 Handwritten Notes

Solutions & Colligative Properties — Complete Handwritten Notes for NEET & JEE Main

Master one of the highest-scoring chapters of Class 12 Chemistry with topper-quality handwritten notes covering types of solutions, concentration terms, Raoult's Law, ideal & non-ideal solutions, all four colligative properties, Van't Hoff factor and 50+ solved numericals — all in one place.

📄 Complete Handwritten Notes PDF

📁 Browse All Chapter Resources

📘 What's in the Syllabus? (NEET vs JEE Main)

Solutions & Colligative Properties is one of the most scoring chapters of Class 12 Chemistry. It carries 3-5 marks in every NEET and JEE Main exam, with most questions being direct formula-based numericals. Let's compare both syllabi:

🩺 NEET Syllabus

Types of solutions
Concentration terms — molarity, molality, mole fraction
Solubility of solids & gases
Raoult's Law & its applications
Ideal & non-ideal solutions
Colligative properties — RVP, elevation in BP, depression in FP, osmotic pressure
Determination of molar masses
Van't Hoff factor

🎯 JEE Main Syllabus

Solubility — Henry's Law & its applications
Liquid-Liquid solutions — Raoult's Law
Types of non-ideality — positive & negative deviations
Azeotropes — maximum & minimum boiling
All four colligative properties with derivations
Abnormal molar mass & Van't Hoff factor
Numerical problems on degree of dissociation/association

💡 Pro Tip for Aspirants

This chapter is a guaranteed 3-5 marks in NEET/JEE Main. The numericals are formula-based and very scoring. Master the four colligative property formulas and Van't Hoff factor — you'll never lose a mark from this chapter!

📌 Topics Covered in These Notes

Our handwritten notes are structured to cover every single sub-topic from NCERT Class 12 Chemistry Chapter 2. Here's a quick overview:

🧪Types of Solutions9 types explained

📊Concentration TermsM, m, x, %

💧SolubilitySolids & gases

🌬️Henry's Lawp = K_H × x

⚗️Raoult's LawVolatile solutes

📈Ideal SolutionsNo deviation

📉Non-Ideal+ve & -ve deviation

🌡️AzeotropesMax & min boiling

📉RVPRelative lowering

🔥Elevation in BPΔTb = Kb·m

❄️Depression in FPΔTf = Kf·m

💧Osmotic Pressureπ = CRT

⚡Van't Hoff Factori = normal/observed

🧮Numericals50+ solved

🎯PYQsLast 10 years

✏Short TricksQuick solve

1. Types of Solutions

A solution is a homogeneous mixture of two or more components. The component present in the largest amount is called the solvent, and the others are called solutes. Based on the physical state of solvent and solute, there are 9 types of solutions:

Solvent	Solute	Example
Gas	Gas	Air (N₂ + O₂)
Gas	Liquid	Water vapour in air
Gas	Solid	Camphor in N₂ (rare)
Liquid	Gas	Soda water (CO₂ in water)
Liquid	Liquid	Alcohol in water
Liquid	Solid	Sugar in water, NaCl in water
Solid	Gas	H₂ in palladium
Solid	Liquid	Amalgam of Hg with Na
Solid	Solid	Alloys (brass, bronze)

📌 NCERT Key Point

Most important solutions for NEET/JEE are liquid solutions (liquid solvent) — especially solid-in-liquid and liquid-in-liquid. Focus maximum energy here!

2. Concentration Terms — All Formulas

Concentration of a solution expresses the amount of solute dissolved in a given amount of solvent or solution. You must memorise all these formulas:

🧮 Concentration Formulas

📐 Mass % (w/w): (Mass of solute / Mass of solution) × 100
📐 Volume % (v/v): (Volume of solute / Volume of solution) × 100
📐 Mass by Volume % (w/v): (Mass of solute / Volume of solution) × 100 (used in pharmacy)
📐 Mole Fraction (x): x₁ = n₁/(n₁ + n₂) ; x₁ + x₂ = 1
📐 Molarity (M): M = Moles of solute / Volume of solution (in L)
📐 Molality (m): m = Moles of solute / Mass of solvent (in kg)
📐 Molarity ↔ Molality: m = (1000 × M) / (1000 × d - M × M₂) where d = density
📐 Parts per million (ppm): (Mass of solute / Mass of solution) × 10⁶

⚠️ Exam Trap Alert

Molarity changes with temperature (because volume changes), but molality does NOT change with temperature (because mass is independent of temperature). This is why molality is preferred for precise work. This is a favourite NEET question!

3. Solubility

Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a particular temperature.

🔹 Solubility of Solids in Liquids

For endothermic dissolution (ΔH > 0): Solubility increases with temperature (e.g., KNO₃, NaCl)

For exothermic dissolution (ΔH < 0): Solubility decreases with temperature (e.g., Ce₂(SO₄)₃, CaSO₄)

Pressure has negligible effect on solubility of solids in liquids.

🔹 Solubility of Gases in Liquids — Henry's Law

The solubility of a gas in a liquid depends on pressure and temperature:

🌬️ Henry's Law

📐 p = K_H × x
Where: p = partial pressure of gas, K_H = Henry's constant, x = mole fraction of gas in solution
📐 Higher K_H → Lower solubility (at same pressure)
📐 Temperature ↑ → K_H ↑ → Solubility ↓
📐 Pressure ↑ → Solubility ↑

🔹 Applications of Henry's Law

✓

Carbonated beverages: CO₂ is sealed at high pressure to increase solubility.

✓

Scuba diving: At high pressure underwater, more N₂ dissolves in blood. On ascending, it forms bubbles → bends (decompression sickness). He + O₂ mixture is used to avoid this.

✓

High altitude: Low partial pressure of O₂ → low concentration in blood → anoxia (inability to think clearly).

4. Raoult's Law

Raoult's Law is the solution counterpart of Henry's Law. It applies to ideal solutions and solutions of volatile liquids.

⚗️ Raoult's Law Formulas

📐 For volatile solute: p₁ = p₁° × x₁ (partial vapour pressure = mole fraction × pure vapour pressure)
📐 Total vapour pressure: P_total = p₁ + p₂ = p₁°x₁ + p₂°x₂
📐 For non-volatile solute: P_solution = p₁° × x₁ (only solvent contributes)
📐 Relative lowering of vapour pressure: (p₁° - p₁)/p₁° = x₂ (mole fraction of solute)
📐 (p₁° - p₁)/p₁° = n₂/(n₁ + n₂) = (w₂/M₂) / (w₁/M₁ + w₂/M₂)

💡 Memory Trick

"Henry's Law = solute perspective (p = K_H × x), Raoult's Law = solvent perspective (p = p° × x)". Both have the same form but different constants. Henry's constant is K_H, Raoult's constant is p°.

5. Ideal & Non-Ideal Solutions

Property	Ideal Solutions	Non-Ideal Solutions
Obeys Raoult's Law	Yes, at all concentrations	No, deviates
ΔH_mix	= 0	≠ 0
ΔV_mix	= 0	≠ 0
Interactions	A-B = A-A = B-B	A-B ≠ A-A or B-B
Examples	benzene + toluene, n-hexane + n-heptane	ethanol + water, acetone + CS₂

🔹 Types of Deviations

Property	Positive Deviation	Negative Deviation
Raoult's Law	p_observed > p_calculated	p_observed < p_calculated
Interactions	A-B < A-A, B-B	A-B > A-A, B-B
ΔH_mix	> 0 (endothermic)	< 0 (exothermic)
ΔV_mix	> 0 (volume increases)	< 0 (volume decreases)
Azeotrope	Minimum boiling azeotrope	Maximum boiling azeotrope
Examples	ethanol + acetone, benzene + methanol	chloroform + acetone, phenol + aniline

⚠️ Exam Trap Alert

Azeotropes are binary mixtures with the same composition in liquid and vapour phase and boil at a constant temperature. They CANNOT be separated by fractional distillation. This is a classic NEET/JEE question!

6. Colligative Properties — The Heart of This Chapter

Colligative properties are properties of solutions that depend only on the number of solute particles, not on their nature. There are four colligative properties:

🧮 All Four Colligative Property Formulas

📉 1. Relative Lowering of Vapour Pressure (RLVP):
📐 (p° - p)/p° = x₂ = n₂/(n₁ + n₂)
📐 For dilute solution: (p° - p)/p° ≈ n₂/n₁ = (w₂ × M₁)/(w₁ × M₂)
🔥 2. Elevation of Boiling Point (ΔTb):
📐 ΔTb = Kb × m (m = molality)
📐 Tb(solution) = Tb(solvent) + ΔTb
📐 Kb = R × Tb² × M₁ / (1000 × ΔH_vap) (ebullioscopic constant)
❄️ 3. Depression of Freezing Point (ΔTf):
📐 ΔTf = Kf × m (m = molality)
📐 Tf(solution) = Tf(solvent) - ΔTf
📐 Kf = R × Tf² × M₁ / (1000 × ΔH_fus) (cryoscopic constant)
💧 4. Osmotic Pressure (π):
📐 π = C × R × T (C = molarity, R = 0.0821 L·atm/mol·K)
📐 π = (n/V) × R × T = (w₂/M₂) × (RT/V)

🔹 Common Values to Remember

b (K·kg/mol)f (K·kg/mol)b (°C)f (°C)

Solvent
Water	0.52	1.86	100	0
Benzene	2.53	5.12	80.1	5.5
Camphor	5.61	39.7	204	179.8

💡 Memory Trick

"Kb for water = 0.52, Kf for water = 1.86" — remember "0.52" (boiling) and "1.86" (freezing). Kf is always larger than Kb for the same solvent. Camphor has the highest Kf (39.7) — used in Rast's method for molar mass determination.

7. Van't Hoff Factor (i)

When solutes dissociate (like NaCl → Na⁺ + Cl⁻) or associate (like 2CH₃COOH → (CH₃COOH)₂), the number of particles changes. This affects colligative properties. The Van't Hoff factor i accounts for this:

⚡ Van't Hoff Factor Formulas

📐 i = Normal molar mass / Observed molar mass
📐 i = Observed colligative property / Calculated colligative property
📐 i = Total moles of particles after dissociation/association / Initial moles of solute
📐 For dissociation: i = 1 + (n-1)α (where n = number of ions, α = degree of dissociation)
📐 For association: i = 1 - (1 - 1/n)α (where n = number of molecules associating)
📐 Modified colligative formulas:
📐 ΔTb = i × Kb × m
📐 ΔTf = i × Kf × m
📐 π = i × C × R × T
📐 (p° - p)/p° = i × x₂

🔹 Common Values of i

i (complete dissociation)Particles

Solute
Glucose, Urea, Sucrose	1	No dissociation
NaCl, KCl, KNO₃	2	Na⁺ + Cl⁻
CaCl₂, BaCl₂, MgCl₂	3	Ca²⁺ + 2Cl⁻
Na₂SO₄, K₂SO₄	3	2Na⁺ + SO₄²⁻
AlCl₃	4	Al³⁺ + 3Cl⁻
K₄[Fe(CN)₆]	5	4K⁺ + [Fe(CN)₆]⁴⁻
CH₃COOH (in benzene)	0.5	Dimer formation

⚠️ Common Mistake

Students often forget that i = 0.5 for acetic acid in benzene (not 2) because it forms a dimer through hydrogen bonding. This is a very common NEET trap!

8. Important Numerical Examples

📝 Example 1: Molar Mass from Osmotic Pressure

Q: 1.5 g of an unknown solute dissolved in 500 mL of water gives an osmotic pressure of 0.6 atm at 27°C. Find molar mass.
Sol: π = (w₂/M₂) × (RT/V) → 0.6 = (1.5/M₂) × (0.0821 × 300 / 0.5) → M₂ = 123.15 g/mol

📝 Example 2: Depression in Freezing Point

Q: Find the freezing point of a solution containing 10 g of NaCl in 500 g of water. (Kf = 1.86 K·kg/mol)
Sol: m = (10/58.5) / 0.5 = 0.342 mol/kg; i = 2; ΔTf = 2 × 1.86 × 0.342 = 1.27°C
Tf = 0 - 1.27 = -1.27°C

📝 Example 3: Van't Hoff Factor

Q: 0.1 M K₂SO₄ solution is 80% dissociated. Find i.
Sol: K₂SO₄ → 2K⁺ + SO₄²⁻ (n = 3); i = 1 + (3-1)×0.8 = 2.6

🎯 Frequently Asked PYQs from Solutions

Molar mass from osmotic pressure NEET 2024
Van't Hoff factor for Na₂SO₄ JEE Main 2024
Henry's Law — solubility of gas NEET 2023
Elevation in boiling point numerical JEE Main 2023
Ideal vs non-ideal solution NEET 2022
Raoult's Law — relative lowering of VP JEE Main 2022
Depression in freezing point NEET 2021
Azeotrope definition & examples JEE Main 2021
Positive vs negative deviation NEET 2020
Degree of dissociation from i JEE Main 2019

❌ Common Mistakes Students Make

✗

Using molarity instead of molality in ΔTb and ΔTf formulas. ✓ Correct: ΔTb = Kb × m (molality), not M (molarity). Only osmotic pressure uses molarity: π = C × R × T.

✗

Forgetting to multiply by i for ionic solutes. ✓ Correct: For NaCl, CaCl₂, K₂SO₄ etc., always use ΔT = i × K × m. Don't forget i!

✗

Writing i = 2 for CH₃COOH in benzene. ✓ Correct: Acetic acid in benzene forms a dimer, so i = 0.5 (not 2). In water, it partially dissociates so i is between 1 and 2.

✗

Confusing Kb (ebullioscopic) with Kf (cryoscopic) values. ✓ Correct: Kb for water = 0.52, Kf for water = 1.86. Kf is always larger than Kb for the same solvent.

✗

Thinking molarity is independent of temperature. ✓ Correct: Molarity changes with temperature (volume changes), but molality does not (mass is constant).

✗

Writing Raoult's Law as p = K_H × x for the solvent. ✓ Correct: Raoult's Law for solvent: p = p° × x. Henry's Law for solute: p = K_H × x. Don't mix them!

16+Major Topics Covered

50+Formulas & Numericals

100%NCERT Aligned

📥 Download Complete Solutions & Colligative Properties Notes

Get the full PDF with all diagrams, solved examples, PYQs and formula sheets — perfect for last-minute revision before NEET or JEE Main.

⬇️ Download Full PDF Now

❓ Frequently Asked Questions

Yes! These notes cover 100% of the NCERT syllabus for Solutions & Colligative Properties, plus additional numericals and PYQs. For JEE Advanced, you may need to practice extra problems on degree of dissociation separately.

On average, 2-3 questions come from this chapter in both NEET and JEE Main every year. Most are formula-based numericals on colligative properties and Van't Hoff factor, making this a very high-scoring chapter.

Solutions carries about 4-5 marks in board exams and 3-5 marks in competitive exams. It's a short chapter but very high-scoring if prepared well.

Colligative properties and Van't Hoff factor are the most frequently asked topics. Master these and you'll score full marks. Raoult's Law and Henry's Law are also very important.

Yes! The PDF is embedded above — you can view it directly or download it from Google Drive. It's completely free and works offline.

Solutions is actually one of the easiest chapters if you memorise the formulas and practice numericals. Start with concentration terms, then move to Raoult's Law, and finally tackle colligative properties. With 3-4 days of focused study, you can master this chapter!

🎓 Final Thoughts

Solutions & Colligative Properties is one of the most scoring chapters in Class 12 Chemistry. With a little effort, you can easily secure full marks from this chapter in both NEET and JEE Main. The key is to memorise the formulas, understand the Van't Hoff factor concept, and practice at least 30 numericals from colligative properties.

Our Class 12 Chemistry Chapter-2 Solutions & Colligative Properties Handwritten Notes are designed exactly keeping this strategy in mind — concise, to-the-point, and exam-focused. Whether you're revising a day before the exam or studying the chapter for the first time, these notes will help you save time and score more.

🚀 Study Strategy for Solutions

Day 1: Concentration terms & solubility → Day 2: Raoult's Law & ideal/non-ideal solutions → Day 3: All four colligative properties → Day 4: Van't Hoff factor & solve 30+ numericals. Follow this 4-day plan and you'll master the chapter!

📚 Explore More Notes:

🧪 Chemistry Notes 📝 Revision Notes 🩺 NEET Notes 🎯 JEE Notes