Chapter 1 – Solutions & Their Properties

Vocabulary flashcards that cover fundamental terms, laws, concentration units, and properties related to solutions, their behaviour, and colligative effects as presented in the lecture notes.

Solution

A homogeneous mixture of two or more pure substances.

Solute

The component present in lesser amount; the substance dissolved in a solution.

Solvent

The component present in larger amount that dissolves the solute and determines the solution’s physical state.

Aqueous Solution

A solution in which water acts as the solvent.

Non-aqueous Solution

A solution whose solvent is any liquid other than water (e.g., iodine in alcohol).

Saturated Solution

A solution that cannot dissolve any additional solute at a given temperature.

Unsaturated Solution

A solution that can still dissolve more solute at the same temperature.

Mass Percentage (w/w)

Mass of solute in the solution/Total mass of the solution × 100

Volume Percentage (v/v)

Volume of solute / Total volume of solution × 100.

Mass by Volume Percentage (w/v)

Mass of solute / Volume of solution × 100; widely used in pharmacy.

Parts Per Million (ppm)

Parts of a component per 10⁶ parts of solution; used for trace concentrations.

Mole Fraction (Χ)

Moles of a component divided by total moles of all components; ΧA + ΧB = 1 for a binary solution.

Molarity (M)

Moles of solute per litre of solution; temperature dependent.

Molality (m)

Moles of solute per kilogram of solvent; temperature independent.

Normality (N)

Gram-equivalents of solute per litre of solution; useful in acid-base reactions.

Henry’s Law

The solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid (p = K_H Χ).

Solubility

Maximum amount of solute dissolvable in 100 g of solvent at a specified temperature.

Raoult’s Law

For volatile liquids, each component’s partial vapour pressure equals the product of its mole fraction and its pure vapour pressure (PA = P°A Χ_A).

Ideal Solution

A mixture that obeys Raoult’s law over all compositions and temperatures; ΔHmix = 0 and ΔVmix = 0.

Non-ideal Solution

A mixture that deviates from Raoult’s law due to differing intermolecular forces; exhibits positive or negative deviation.

Positive Deviation

Vapour pressure higher than predicted; A–B interactions weaker than A–A or B–B (e.g., ethanol + water).

Negative Deviation

Vapour pressure lower than predicted; A–B interactions stronger than A–A or B–B (e.g., chloroform + acetone).

Azeotrope

A constant-boiling mixture whose liquid and vapour phases have identical composition during distillation.

Minimum-Boiling Azeotrope

Formed by solutions with large positive deviation; boils at temperature lower than either component (e.g., ethanol–water).

Maximum-Boiling Azeotrope

Formed by solutions with large negative deviation; boils at temperature higher than either component (e.g., HNO₃–H₂O).

Colligative Properties

Solution properties that depend only on particle number, not nature—relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, and osmotic pressure.

Relative Lowering of Vapour Pressure

(P° – P) ⁄ P°; numerically equal to solute mole fraction for dilute solutions.

Elevation of Boiling Point (ΔT_b)

Increase in boiling temperature when a non-volatile solute is added; ΔTb = Kb m.

Depression of Freezing Point (ΔT_f)

Decrease in freezing temperature on adding solute; ΔTf = Kf m.

Ebullioscopic Constant (K_b)

Molal elevation constant used in ΔTb = Kb m.

Cryoscopic Constant (K_f)

Molal depression constant used in ΔTf = Kf m.

Osmosis

Net flow of solvent through a semipermeable membrane from pure solvent to solution.

Osmotic Pressure (π)

The pressure required to stop osmosis; for dilute solutions π = C R T.

Reverse Osmosis

Process in which pressure greater than osmotic pressure is applied to force solvent out of a solution, purifying it.

Abnormal Molecular Mass

Molar mass calculated from colligative data differs from theoretical due to solute association or dissociation.

Van’t Hoff Factor (i)

Ratio of observed to calculated colligative property; indicates degree of association or dissociation (i = observed / normal).

Hypertonic Solution

Solution with higher solute concentration (and osmotic pressure) than the solution on the other side of a membrane.

Hypotonic Solution

Solution with lower solute concentration than the opposing solution across a membrane.

Isotonic Solutions

Two solutions exerting equal osmotic pressure at a given temperature; no net osmosis occurs.

Vapour Pressure

Pressure exerted by vapour in equilibrium with its liquid at a given temperature.