Playbook
Solutions and Colligative Properties
131 q - 3.17/paper - 3% HARD. The heaviest Chemistry chapter; four of six pages are one idea — a colligative property counts dissolved particles.
- Questions in the bank
- 131
- q/paper (2024–25 papers)
- 3.17
- Tagged HARD
- 3%
- Subtopics
- 6
Strand: Calculate
When you’ll see it
A solute in a solvent and a change in vapour pressure, boiling point, freezing point or osmotic pressure — or a gas dissolving under pressure.
How this chapter is tested
131 q at 3.17 a paper — the heaviest Chemistry chapter on recent papers — and 3% HARD. Four of its six pages are the same idea in four forms: a colligative property depends on how many particles are dissolved, not on what they are. Boiling-point elevation (28 q), vapour-pressure lowering (23 q), osmotic pressure (22 q) and freezing-point depression (16 q) all scale with the van't Hoff factor i.
The other two pages are quick. Henry's law (27 q, with the solution types) is one multiplication, C = K_H·p. The van't Hoff page (15 q) is i from a measured freezing point, or the ratio question 'x K for urea, how much for CaCl₂' — 3x, because CaCl₂ gives three ions.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Colligative formulas
ΔT_b = iK_b·m, ΔT_f = iK_f·m, π = iCRT, and (p° − p)/p° = x₂ (dilute: W₂M₁/(M₂W₁)).
The van't Hoff factor
i = particles per formula unit for a strong electrolyte (NaCl 2, CaCl₂ 3, AlCl₃ 4); i = observed ÷ normal colligative value otherwise.
Henry's law
Solubility C = K_H·p. Check whether K_H is given per bar or its reciprocal.
Solution types
Name the solute and solvent phases: iodine in air is solid in gas; camphor in N₂ likewise.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Forgetting i for an electrolyte
0.1 m NaCl lowers the freezing point about twice as much as 0.1 m glucose. Leaving i = 1 gives the glucose answer, and it is printed.
Molality against molarity
ΔT uses molality (per kg of solvent); π uses molarity (per litre of solution). Mixing them shifts the answer by the solution's density.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Solutions and Colligative Properties notesDrill every solutions and colligative properties question
131 questions from the bank, scoped to 6 bundled subtopics.
Drill one subtopic at a time
The 6 subtopics this playbook covers, in catalog order.
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