Eduvista · Class 12 Chemistry
Solutions
A focused lesson and practice set. This page covers the concepts listed below; it is not a claim of complete chapter or syllabus coverage.
Learn the essentials
Concentration
Molarity M is moles of solute per litre of solution; molality m is moles of solute per kilogram of solvent. Molarity can change with temperature because volume changes.
Raoult's law
For an ideal solution, the partial vapour pressure of a volatile component equals its mole fraction times its pure-component vapour pressure.
Colligative properties
Relative lowering of vapour pressure, elevation of boiling point, depression of freezing point and osmotic pressure depend on the number of solute particles in a dilute solution.
Worked example
Find molarity when 0.5 mol solute is present in 250 mL of solution.
- Convert solution volume: 250 mL = 0.250 L.
- Use M = moles of solute / litres of solution.
- M = 0.5 / 0.250 = 2.0 mol L⁻¹.
Memory trick
Remember M uses solution volume; m uses solvent mass. Capital M → measuring flask; small m → mass of solvent.
Common mistakes
- Using mass of solution instead of mass of solvent for molality.
- Using mL directly in molarity without converting to litres.
- Ignoring dissociation or association when interpreting particle-dependent properties.
Practice recall
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Original practice quiz
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Quick revision sheet
- M = n(solute)/V(solution in L).
- m = n(solute)/mass(solvent in kg).
- Mole fraction is moles of a component divided by total moles.
- Colligative effects depend on effective solute particle count.
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