Chemistry Notes: Vapor Pressure, Solubility, and Colligative Properties

Vocabulary flashcards covering key concepts from the lecture notes on vapor pressure, phase changes, and colligative properties.

Clausius–Clapeyron equation

ln(P1/P2) = (ΔHvap/R)(1/T1 − 1/T2); relates vapor pressure to temperature for phase changes and is used to estimate how P changes with T.

Vapor pressure

The pressure exerted by a vapor in equilibrium with its liquid or solid at a given temperature.

Enthalpy of vaporization (ΔHvap)

The energy required to vaporize one mole of a substance at a given temperature (typically expressed in kJ/mol).

Natural logarithm (ln)

Logarithm with base e; ln(x) uses the base e.

Common logarithm (log10)

Logarithm with base 10; log(x) uses the base 10.

Gas constant (R)

8.314 J/(mol·K); appears in gas-law equations and in Clausius–Clapeyron calculations.

P1, P2, T1, T2 (vapor-pressure problem labeling)

P1 and P2 are vapor pressures at temperatures T1 and T2; temperatures are used in the Clausius–Clapeyron equation.

Kelvin (K)

Absolute temperature scale; T(K) = T(°C) + 273.15.

Molality (m)

Concentration unit: m = moles of solute per kilogram of solvent; used in colligative-property equations.

Colligative properties

Properties that depend on the number of solute particles, not their identity: freezing point depression, boiling point elevation, osmotic pressure, and vapor-pressure lowering.

Freezing point depression (ΔTf)

ΔTf = i·Kf·m; i is the van't Hoff factor, Kf is the cryoscopic constant, m is molality.

Boiling point elevation (ΔTb)

ΔTb = i·Kb·m; i is the van't Hoff factor, Kb is the ebullioscopic constant, m is molality.

Osmotic pressure (π)

π = i·M·R·T (pi equals van't Hoff factor times molarity times gas constant times temperature); measures osmotic pressure.

Henry's Law

C = kH · P; the concentration of a dissolved gas is proportional to its partial pressure in the gas phase; kH is Henry's constant.

Solute vs Solvent

Solute is the substance dissolved; solvent is the medium in which the solute dissolves.

Solubility

The maximum amount of solute that can dissolve in a solvent at a given temperature.

Effect of temperature on solubility (solids vs gases)

Solubility of most solids increases with temperature; for gases, solubility typically decreases with temperature.

Effect of pressure on gas solubility

Increasing pressure generally increases the solubility of gases in liquids (Henry's law context, e.g., carbonation).

Energy unit conversion

1 kJ = 1000 J; used when converting ΔHvap from kJ/mol to J/mol.

Kelvin conversion reminder

To convert Celsius to Kelvin: T(K) = T(°C) + 273.15.