Topic 3: Electrolytic Processes

Alice Clayden
Mind Map by , created over 6 years ago

Chemistry Mind Map on Topic 3: Electrolytic Processes, created by Alice Clayden on 04/25/2013.

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Alice Clayden
Created by Alice Clayden over 6 years ago
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Topic 3: Electrolytic Processes
1 Molten/ aqueous ionic substances (e.g copper chloride(aq))- charged ions migrate to the electrode of opposite charge and solution is separated
1.1 At anode (+) - negative ions (anions) lose electrons and are oxidised, they become atoms again. e.g. chloride ions into chlorine.
1.2 At cathode (-) - positive ions (cations) gain electrons and are reduced, they become atoms again. e.g. copper ions turn to solid copper.
1.3 Half equations show what happens at the electrodes. e.g. anode- 2Cl- > Cl2 + 2e-, cathode - Cu+ + e- > Cu
2 Electrolysis of sodium chloride: (salt water/ brine) electrolyte is water- ions present are Na+, Cl-, H+, OH-
2.1 Sodium (Na+) and Hydrogen (H+) ions migrate towards the cathode. H gas is given off as H+ ions gain electrons (reduction). Sodium stays in solution.
2.1.1 Hydrogen used for making ammonia and margarine
2.2 Hydroxide (OH-) and Chloride (Cl-) ions migrate to the anode. Cl gas given off as Cl- ions lose electrons (oxidation). Hydroxide stays in solution
2.2.1 Chlorine used for making bleaches, disinfectants, paints and plastics
2.3 Sodium hydroxide solution is produced (NaOH)- used in making soap, paper and synthetic fibres
3 Sodium metal can be obtained if molten sodium chloride is electrolysed- Na at the cathode, Cl at the anode
3.1 uses of sodium- nuclear reactants as a coolant and in street lights to make them yellow
3.2 Na+ + e- > Na
4 Electroplating
4.1 Coating an object e.g. silver cutlery with a thin layer of metal by electrolysis
4.2 Why do this? used to make a cheaper metal object e.g. stainless steel cutlery look more attractive and shiny by coating in silver.
4.2.1 Jewellery is often gold plated, and tins and car wheels are plated to protect them from corrosion
4.3 the object being plated is used as the cathode and the metal being used is the anode
4.3.1 Positive metal migrates over and is reduced, forms a solid mteal layer on the object
4.3.1.1 the electrolyte has to contain the relevant metal ions e.g. copper sulfate to coat a nail in copper
5 Purification of copper
5.1 Active electrodes used- anode is impure copper, cathode is a very small strip of pure copper
5.2 positively charged copper ions (Cu2+) move from the anode to the cathode where they reduce back to copper atoms and they form solid pure copper.
5.2.1 impurities are not attracted to the cathode and so are left behind and fall to the bottom of the electrolyte. It is called sludge and has some uses
5.2.1.1 it may contain valuable metallic elements e.g. gold, silver, platinum
5.3 copper sulfate solution used as electrolyte

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