Chemistry · Ch 9 — Solutions
Introduction
Introduction
Look closely at almost anything around you -- sea water, the air you breathe, even a brass fitting -- and you'll find it is rarely a pure substance. Most matter is a mixture, and when that mixture is uniform right down to the molecular scale, chemists call it a solution.
What this unit sets out to do. By the end of it you should be able to:
- describe how different types of solutions form;
- express the concentration of a solution in different units, and prepare a solution of a required concentration by diluting a stock solution;
- state Henry's law and Raoult's law;
- explain why real solutions deviate from Raoult's law;
- correlate the colligative properties of a solution with the molar mass of its solute;
- explain abnormal colligative properties;
- define the van't Hoff factor, and use it to calculate the degree of dissociation or association of a solute.
Note
Francois-Marie Raoult built his career studying exactly this kind of solution behaviour. His first research paper described how a dissolved solute depresses a solution's freezing point, and he later derived the relationship between a solution's vapour pressure and its solute's molecular weight -- the law that carries his name and anchors much of this unit.