Chemistry Science Investigation B Townend 10R 28/06/01 Electrolysis Plan
Scientific Knowledge
Most inorganic and some organic chemical compounds, when in a molten state or when dissolved in water or other liquids, become ionised; that is, their molecules become dissociated into positively and negatively charged components, which have the property of conducting an electric current. If a pair of electrodes is placed in a solution of an electrolyte, or an ionisable compound, and a source of direct current is connected between them, the positive ions in the solution move toward the negative electrode and the negative ions toward the positive. On reaching the electrodes, the ions may gain or lose electrons and be transformed into neutral atoms (those with a full outer shell) or molecules, the nature of the electrode reactions depending on the potential difference, or voltage, applied.
The action of a current on an electrolyte can be understood from a simple example. If the salt copper sulphate is dissolved in water, it dissociates into positive copper ions and negative sulphate ions. When a potential difference is applied to the electrodes, the copper ions move to the negative electrode, are discharged, and are deposited on the electrode as metallic copper. The sulphate ions, when discharged at the positive electrode, are unstable and combine with the water of the solution to form sulphuric acid and oxygen. Such decomposition caused by an electric current is called electrolysis.
