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CALCULATING ON THE SIDE OF SUCCESS – Module P(2030): QUANTITATIVE ELECTROLYSIS

 T.  ELECTROCHEMISTRY & ELECTROLYSIS 

 T1.  INTRODUCTION  

Electrical Nature of Matter

The view that chemical combination between atoms is electrical in nature was suggested as early as 1800 following experiments by Nicholson and Carlisle who passed electricity through a variety of molten and aqueous salts, managing in the process to decompose water into hydrogen and oxygen.

In 1833, Faraday’s laws of electrolysis formalised the factors affecting the mass of a material deposited during electrolysis. Remember of course, at this early stage, virtually nothing was known about atoms themselves, let alone their internal structure.

Electric charge, Q

Electric charge can be either positive or negative.
Opposite charges attract each other and like charges repel each other.

Electric charge (quantity symbol Q) is measured in coulombs (SI unit symbol C).

Electric current, I

(a) Conductors

Electricity is a form of energy; an electric current can be considered as a flow of mobile charge carriers in a material.  Conductors are materials which allow electricity to pass through them easily,
e.g., all metals, graphite and black phosphorus.  These have a low electrical resistance.
N.B. the resistance of metals increases with increasing temperature,
i.e., they become less good electrical conductors – this defines a metal.

(b) Insulators

These are materials which do not (easily) allow electricity to pass through them and they possess
a high electrical resistance, e.g., non-metals and covalent compounds.

The plastic PTFE - polytetrafluoroethane, (F-C-F)n - is particularly effective, as is sulphur hexafluoride, SF6(g), which finds use as a gaseous insulator in high-voltage applications.
In these materials the valence electrons are firmly bound either in bonds or by atoms and so
no mobile charge carriers are available for electrical conduction.

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