Solutions, Concentrations, and Colligative Properties

Flashcards for Chemistry Exam Review

Solution

A homogeneous mixture.

Solvent

The substance doing the dissolving.

Solute

The substance being dissolved.

Molarity (M)

Moles of solute per liter of solution. M = mol/L

Colligative Properties

Properties of a solution that depend on the concentration, but not the identity, of the solute particles dissolved in the solvent; Osmotic Pressure, Vapor Pressure Lowering, Freezing Point Depression, Boiling Point Elevation.

Osmosis

A physical process by which a solvent spontaneously flows through a semipermeable membrane from a more dilute to a more concentrated solution until it reaches equilibrium.

Semipermeable Membrane

A selective membrane that is selective typically by size.

Osmotic Pressure

The pressure applied across a semipermeable membrane to stop the flow of solvent in osmosis. Π= iMRT

Van’t Hoff Factor (i)

Used to account for all of the solute particles that are produced when the solute is placed in solution. i = (mol particle in solution) / (mol particles dissolved)

Vapor Pressure

The pressure exerted by a gas on its liquid surface when the gas is in equilibrium with its liquid phase at a given temperature. Liquids that have a significant vapor pressure (more in gas phase) at a given temperature are considered volatile.

Henry’s Law

The concentration of a gas dissolved in a solution is proportional to its partial pressure above the solution. Cgas = kHPgas

Raoult’s Law

The vapor pressure of the solution is equal to the mole fraction of solvent times the partial pressure of the solvent Psolution = XsolventP° solvent

Molality (m)

Moles of solute per kilograms of solvent. m = (mol solute) / (kg solvent)

Freezing Point Depression

The addition of a solute to a pure solvent will lower the freezing point of the solution. ΔTfp = iKfm

Boiling Point Elevation

The addition of a solute to a pure solvent will increase the boiling point of the solution. ΔTbp = iKbm