Solutions
Free NCERT-aligned study resource for the 2026–27 academic session.
CBSE weightage: 7 marks. This unit is part of the official 70-mark Chemistry theory course for 2026–27. citeturn0search11
1. What You Need to Learn
Types of solutions; concentration terms; solubility; vapour pressure; ideal and non-ideal solutions; colligative properties; determination of molar mass; abnormal molar masses.
2. Core Concepts & Formulae
Molarity (M) = moles of solute / volume of solution in L. Molality (m) = moles of solute / mass of solvent in kg. Mole fraction is moles of a component divided by total moles. Raoult’s law relates vapour pressure to mole fraction for ideal solutions. Elevation in boiling point: ΔTb = Kb m; depression in freezing point: ΔTf = Kf m; osmotic pressure: π = CRT.
3. Common Mistakes
Do not confuse molarity with molality; temperature changes volume and therefore molarity, while molality is temperature-independent. For colligative-property questions, identify whether the solute associates or dissociates and use the van’t Hoff factor i when required.
4. Exam-Focused Practice
- A solution contains 0.5 mol solute in 2 kg solvent.
- Find its molality.
- A 0.10 M solution is diluted to twice its volume; find the new molarity.
- Explain why molality is preferred for temperature-based calculations.
5. Quick Revision Checklist
- Can you define the key terms without looking at the book?
- Can you explain the main trend/reaction/mechanism with a reason?
- Can you solve a numerical or predict a product independently?
- Can you answer an application or competency-based question?