Chemistry Solutions: Types, Concentration & Colligative Properties: quick revision, 17 bites

What Makes a Solution: Solute + Solvent

Two parts, one uniform phase.

Takeaway. A solution is homogeneous at the particle level — solute and solvent cannot be distinguished or filtered apart.

Types of Solutions by Physical State

Nine combinations, one concept.

Takeaway. Any of the three states can act as solute or solvent — the physical state of the solution is that of the solvent.

Concentration: Mass %, ppm, Mole Fraction

Four ways to say 'how much'.

Takeaway. Mass % and ppm are mass-based; mole fraction is mole-based and dimensionless.

Molarity vs Molality

M vs m — one letter, big difference.

Takeaway. Use molality for colligative properties because it does not change with temperature.

Normality and Equivalent Concept

Equivalents, not moles.

Takeaway. Normality depends on the reaction — the same solution can have different N in different reactions.

Solubility: Saturated, Unsaturated, Supersaturated

How much can dissolve?

Takeaway. Temperature and pressure shift solubility in opposite ways for solids vs gases.

Henry's Law: Gas Solubility vs Pressure

More pressure, more fizz.

Takeaway. Higher pressure above a liquid → more gas dissolves; lower pressure → gas escapes.

Raoult's Law for Ideal Solutions

Vapour pressure follows mole fraction.

Takeaway. Raoult's law is the foundation for all colligative property calculations.

Ideal vs Non-Ideal Solutions

Positive or negative deviation?

Takeaway. Deviation direction tells you whether A–B forces are weaker or stronger than pure-component forces.

Colligative Properties: Depend on Count, Not Identity

Number of particles rules.

Colligative properties depend only on the **number of solute particles**, not on their chemical nature.

Takeaway. All four colligative properties scale with the number of dissolved particles.

Relative Lowering of Vapour Pressure

Solute lowers the vapour pressure.

Takeaway. Relative lowering equals the mole fraction of the solute — a direct link between vapour pressure and composition.

Boiling Point Elevation & Freezing Point Depression

Two shifts, one constant.

Takeaway. K_b and K_f are solvent-specific constants — molality is the only variable you change.

Osmotic Pressure and van't Hoff Equation

Pressure that stops osmosis.

Takeaway. Osmotic pressure is the best method for measuring molar mass of macromolecules because it is measurable at low concentrations.

van't Hoff Factor: Counting Ions

One formula unit, many particles.

Takeaway. For electrolytes, multiply the expected colligative effect by i to account for dissociation.

Molarity vs Molality Mix-Up

Don't swap M and m.

Takeaway. Colligative formulas use molality, not molarity — remember the lowercase m.

Solutions in Everyday Life

Chemistry you can taste.

Takeaway. Colligative properties are the physics behind antifreeze, saline, soda, and desalination.

Exam Tip: Units and Constants

Units win marks.

Takeaway. Matching R to the pressure unit is the most common source of lost marks in solution problems.