Electrolysis
A mindmap for unit 6 of the CIE IGCSE Chemistry specification, 'Electricity and Chemistry'.
- Created by: steph
- Created on: 19-03-13 18:50
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- Electrolysis
- What is it?
- Breaking down of a compound using electricity
- Decomposing
- Ionic compounds
- Molten or dissolved in water
- Breaking down of a compound using electricity
- Electrolysis cell
- Electrolyte
- The compound that conducts electricity and breaks down
- Electrodes
- Carry electric current to and from electrolyte
- Inert
- Graphite or platinum
- Do not react with electrolyte or electrolysis products
- Anode
- Positive electrode
- Halogens or oxygen forms
- Oxidation
- Loss of electrons
- Anions: negative
- Electrolyte
- Anode
- Positive electrode
- Halogens or oxygen forms
- Oxidation
- Loss of electrons
- Anions: negative
- Cathode
- Electrodes
- Carry electric current to and from electrolyte
- Inert
- Graphite or platinum
- Do not react with electrolyte or electrolysis products
- Negative electrode
- Metal or hydrogen forms
- Reduction
- Gain of electrons
- Cations: positive
- Electrodes
- Aqueous sodium chloride
- Ionic compounds in water have more ions
- H+, OH-, Na+, Cl-
- Ion dischange series
- Lower down series = more likely it will be discharged
- Positive ions
- Na +, Mg 2+, Al 3+, H +, Cu 2+
- Negative ions
- SO4 2-, NO3 -, OH -, Cl -, Br -, I -
- Anode
- Chloride ions lose electrons
- 2Cl -(aq) -> Cl2 (g) + 2e -
- Cathode
- Hydrogen ions accept electrons
- 2H +(aq) + 2e - -> H2 (g)
- Na + and OH - remain in solution
- Aqueous sodium hydroxide formed
- Dilute aqueous solutions
- OH - is lower in series than sulfate
- Oxygen discharged
- OH - is lower in series than sulfate
- Refining copper
- Impure copper = anode
- Copper atoms lose valency, form copper ions
- Pure copper = cathode
- Copper ions in electrolyte gain electrons, forms copper
- Copper sulfate (II) solution = electrolyte
- Remains the same colour due to the ions in solution being replaced
- Inert electrodes
- Anode can't lose electrons
- Hydroxide ions discharged, oxygen forms
- Copper deposited at cathode
- Electrolyte loses its colour
- Anode can't lose electrons
- Impure copper = anode
- Electroplating
- Object to be electroplated at cathode
- Plating metal as the anode
- Electrolyte is a solution of ionic compound of the plating metal
- Uses
- Protection from corrosion
- Improving appearance
- Aluminium extraction
- Bauxite = ore
- Dissolved in molten cryolite
- Cathode: aluminium ions gain electrons, reduced to aluminium
- Anode: oxide ions lose electrons, oxidised to oxygen
- What is it?
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