Solutions for NEET UG
Solutions are everywhere, from blood to saline drips to sea water. This chapter covers how to express concentration, Raoult's law, and the colligative properties that depend only on how many particles are dissolved.
ChemistryClass 1272 MCQs2 lessons12 flashcards4 memory tricks
What you'll learn
- Concentration, Henry's law and Raoult's law
Express concentration in different ways and use Henry's and Raoult's laws. - Colligative properties
Calculate boiling point elevation, freezing point depression and osmotic pressure, including the van 't Hoff factor.
Key formulas
| Henry's law (gas solubility) | p = K_H × x |
|---|---|
| Raoult's law | p_A = p°_A × x_A |
| Total pressure of an ideal solution | p = p°_A x_A + p°_B x_B |
| Relative lowering of vapour pressure | (p° − p)/p° = x_solute |
| Boiling point elevation | ΔT_b = i K_b m |
| Freezing point depression | ΔT_f = i K_f m |
| Osmotic pressure | π = iCRT |
Memory tricks
They depend on the number of solute particles, not their identity. 1 M NaCl (i ≈ 2) has about twice the effect of 1 M glucose.
Water moves through a semipermeable membrane from lower to higher solute concentration. Osmotic pressure π = iCRT.
The solubility of a gas is proportional to its partial pressure (p = K_H x). Divers get 'the bends' when dissolved nitrogen comes out of the blood as they surface.
Negative: chloroform + acetone (H-bond forms); lower vapour pressure; maximum-boiling azeotrope. Positive: ethanol + acetone; higher vapour pressure; minimum-boiling azeotrope.
Try 3 NEET-style questions
Q1. The solubility of most solids in liquids increases with temperature when the dissolution process is
- exothermic
- neither endothermic nor exothermic
- endothermic
- independent of temperature
Show answer
Answer: (3) endothermic
By Le Chatelier's principle, if dissolving absorbs heat (endothermic), raising the temperature increases solubility. Pressure has no significant effect on the solubility of solids.
Q2. Which of the following is a natural semipermeable membrane?
- Cellophane
- Glass
- Aluminium foil
- Pig's bladder
Show answer
Answer: (4) Pig's bladder
Natural semipermeable membranes include animal membranes like pig's bladder and parchment. Cellophane is a synthetic semipermeable membrane.
Q3. The osmotic pressure of a 0.1 M solution of a non-electrolyte at 300 K is about (R = 0.0821 L atm K⁻¹ mol⁻¹)
- 0.0246 atm
- 0.246 atm
- 2.46 atm
- 24.6 atm
Show answer
Answer: (3) 2.46 atm
π = CRT = 0.1 × 0.0821 × 300 = 2.46 atm.
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