electrolysis explain the process of electrolysis and its uses


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ElectrolysisExplain the process of electrolysis and its usesElectrolysisA process where electrical energy is transformed into chemical energyIt is not spontaneous, electrical energy must be supplied for a reaction to occurIt has important applications such as:ElectroplatingExtraction of reactive metals such as Na, Al from metal oreIndustrial production of NaOH, Cl2,H2Recharging of car batteries & other rechargeable cellsRefining of copper metals

The process occurring in an electrolytic cell

External Power SupplySource of electrons which can flow. (Current is carried in solution by ions).The process occurring in an electrolytic cell

Two electrodes immersed in a solution of molten reactant (Must be an electrolyte solution that conducts electricity by a flow of ions)The process occurring in an electrolytic cell

Anions will flow in the same direction as the electrons. They are attracted to the Positive anodeAnions lose electrons to become oxidisedThe process occurring in an electrolytic cell

Cations flow in the opposite direction to electronsThey are attracted to the negative Cathode Cations gain electrons to become reducedElectrolysis animationG:\TGHS\Year 13 Chemistry\3.7 redox\Electrolysis.docx

Example Electrolysis of waterHoffmans Voltameter is used for performing electrolysis of water and consists of platinum electrodes. Water is a molecular compound. Pure or distilled water is a non-electrolyte (it contains no charged particles that can carry a current). Therefore, a few crystals of an ionic compound (like sodium chloride to produce ions) or a few drops of a strong acid (hydrochloric acid, sulphuric acid they completely dissociate into ions) need to be added to the water to make it become an electrolyte. The anode and cathode are connected to a battery. The cell produces a small current of the order of a few milliamps and you will see bubbles appearing in the two arms of the voltameter. The anode collects oxygen (the anion is attracted to the positive anode) and the cathode arm collects hydrogen gas (the cation is attracted to the negative cathode)

Extraction of aluminiumAluminium ore is called bauxite. Bauxite contains aluminium oxide, water, iron oxide and other impurities. The purified dry ore, called alumina, is aluminium oxide - Al2O3.The alumina must be molten for electrolysis to work, since the ions are not free to move in the solid statesolid state.

Write equations for the reactions occurring..The steel container is coated with carbon (graphite) and this is used as the negative electrode (cathode). Aluminium oxide (Al2O3) is an ionic compound. When it is melted the Al3+ and O2- ions are free to move and conduct electricity.Electrolysis of the alumina/cryolite solution produces aluminium at the negative cathode and oxygen at the positive anode.