Page 3 - Pharmaceutical analytical chemistry |

Introduction

PROPERTIES OF AQUEOUS SOLUTIONS

Many chemical reactions and, virtually, all biological processes
take place in aqueous media. Some frequently used terms of the aqueous
medium in which reactions take place will be described.

A solution is a homogeneous mixture of two or more substances.
The substance present in smaller proportion is called the solute, and the
substance present in a larger amount is called the solvent. An aqueous
solution can contain more than one kind of solutes. Seawater is a solution
that contains more than sixty different substances.

Electrolytes and Non-electrolytes

All solutes in aqueous solutions can be divided into two categories:
Electrolytes and non-electrolytes.
An electrolyte is a substance that, when dissolved in water, results in a
solution that can conduct electricity, so electrolytes are acids, bases and
salts which furnish ions in solution. Ions are electrically charged so their
solutions conduct electric current hence the name electrolyte.
A non-electrolyte does not conduct electricity when dissolved in water.
Nonelectrolytes are molecular substances, e.g. sucrose and methanol, the
solution process occurs because molecules of the substance mix with
molecules of H2O. Molecules are electrically neutral and cannot carry
out electric current so the solution is electrically non-conducting
Electrolytes can be classified into:
Strong electrolytes:
Acids example: most of the common inorganic acids such as HCl, H2SO4,
HNO3.

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