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Chemistry C2 Part Five
Revision PowerPoint - Big ideas
Electrochemistrymaking elements using
electricity
Electrolysis and ionic compounds
• In electrolysis an electric current is passed through an ionic compound, either molten or in solution. • The compound breaks down into elements.
LEO the LION says GERrrr
• Oxidation happens at the positive electrode.
Negative ions lose electrons. • Reduction happens at
the negative electrode. Positive ions gain electrons.
OXIDATION AND REDUCTION
LEO the lion says GER
Losing Electrons is Oxidation,
Gaining Electrons is Reduction.
Electrolysis in action
• The experiment uses a direct current• The electrodes allow
electrons to enter or leave the solution• The electrolyte is the
ionic compound
Electroplating
Metal objects are electroplated by making them the negative electrode and placing them in a solution of soluble ions. e.g. nickel plating copper
Extracting aluminium
• Aluminium is extracted by electrolysis of molten bauxite dissolved in cryolite.
Brine and the chlor-alkali industry
The electrolysis of brine (salt water) produces sodium hydroxide, chlorine and hydrogen.Sodium
hydroxide is used to manufacture• soaps and
detergents• rayon and
acetate fibres• paper• ceramics
Chlorine is used to manufacture• antiseptics
and disinfectants
• pesticides and weed-killers
• bleachand to kill bacteria in drinking water
Hydrogen is used to manufacture• margarine• ammoniaIt is used in fuel cells and in rocket fuels for space craft