After studying this Unit, you will be able to · describe the formation of different types of solutions; · express concentration of solution in different units; · state and explain Henry’s law and Raoult’s law; · distinguish between ideal and non-ideal solutions; · explain deviations of real solutions from Raoult’s law; · describe colligative properties of solutions and correlate these with molar masses of the solutes; · explain abnormal colligative properties exhibited by some solutes in solutions. In normal life we rarely come across pure substances. Most of these are mixtures containing two or more pure substances. Their utility or importance in life depends on their composition.
For example, the properties of brass (mixture of copper and zinc) are quite different from those of German silver (mixture of copper, zinc and nickel) or bronze (mixture of copper and tin); part per million (ppm) of fluoride ions in water prevents tooth decay, while . ppm causes the tooth to become mottled and high concentrations of fluoride ions can be poisonous (for example, sodium fluoride is used in rat poison); intravenous injections are always dissolved in water containing salts at particular ionic concentrations that match with blood plasma concentrations and so on. In this Unit, we will consider mostly liquid solutions and their formation. This will be followed by studying the properties of the solutions, like vapour pressure and colligative properties.
We will begin with types of solutions and then various alternatives in which concentrations of a solute can be expressed in liquid solution. Almost all processes in body occur in some kind of liquid solutions.