Solutions

What is solution?

A solution is a homogeneous mixture of two (or more) substances, the composition of which may vary between certain limits.
This concept is valid if we take the example of alcohol and water i.e. both the substances are in same phase. But what about sugar syrup, which contains 60% sugar and 40% water? Will the sugar be the solvent? Answers is No, Still the sugar is solute. Then what is the right definition for this case. Well, for heterogeneous substance,

Solvent is that component of the binary mixture which is in same physical state as the solution will be.

A solution consisting of two components is called binary solution. The component which is present in large quantity is called solvent and the component which is small in quantity is called solute. If both components are in same physical state.

Type of Solutions

All the three states of matter (gas, liquid or solid) may behave either as solvent or solute. Depending on the state of solute or solvent, mainly there may be the following seven types of binary solutions.

S.No.	Solute	Solvent	Example
1	Gas	Gas	Air
2	Gas	Liquid	Aerated water (CO₂ + H₂O)
3	Gas	Solid	Hydrogen in palladium
4	Liquid	Liquid	Alcohol in water, benzene in toluene
5	Liquid	Solid	Mercury in zinc amalgam
6	Liquid	Gas	CO₂ dissolved in water
7	Solid	Liquid	Sugar in water, common salt in water
8	Solid	Gas	Smoke
9	Solid	Solid	Various alloys

For a given solution, the amount of the solute dissolved in a unit volume of solution (or a amount of solvent) is termed as the concentration of the solute. Solutions containing relatively high concentration of solute are called concentrated solutions while those of relatively low concentrations of solute are termed as dilute solutions.

What is this chapter all about?

This chapter besides being simple is very important too especially the section dealing with Raoult’s Law , Colligative properties and Van’t Hoff Factor. It begins with modes of expression of strength of solution, followed by vapour pressure of solution, ideal and non ideal solutions, we shall see, how vapour pressure changes with composition (mole fraction) of the components present in the solution. Here, we concentrate only on binary solutions, we shall therefore often be able to simplify equations by making use of relation X_A + X_B = 1, we shall also discuss the properties of solutions which depend upon number of particles of solute (called Colligative Properties) using non volatile solutes and abnormal results due to association or dissociation of electrolytic solute. We will have the systematic study of solution chemistry under following sub topics.

Related Resources

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