Electrolysis
- Created by: Lizzi
- Created on: 19-05-13 15:54
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- Electrolysis
- Electrolysis
- Splits up substances using electricity
- Ionic compounds can only be electrolysed when molten/ in a solution (so ions are free to move around)
- Positive ions move towards negative electrode (cathode)
- Negative ions move to the positive electrode (anode)
- Changes at Electrodes
- Negative ions oxidise (lose electrons) at the anode
- Positive ions reduce (gain electrons) at the cathode
- Aqueous solutions (unless they contain a halide) produce oxygen at the anode
- Aqueous solutions (unless the ions are of a metal less reactive than hydrogen) produce hydrogen at cathode
- Aluminium Extraction
- Aluminium Oxide is electrolysed to manufacture aluminium
- Mixed with cryolite to lower melting point
- Aluminium forms at anode, and oxygen and cathode
- Positive carbon electrodes are replaced as they burn away
- Brine Electrolysis
- Produces three products: Chlorine(g), Hydrogen(g),and sodium hydroxide(l)
- Sodium hydroxide uses: soap, paper, bleach, neutralisation, pH control
- Chlorine uses: kills bacteria in water, bleach, disinfectant, plastics
- Hydrogen uses: margarine, hydrochloric acid
- Half equations: Positive= 2Cl- > Cl2+2e- Negative= 2H+ + 2e- > H2
- Electroplating
- Electroplate objects to: improve appearance, protect, and to use smaller amounts of precious metals
- Object because the negative electrode, plating metal is positive, electrolyte contain positive ions of the plating metal
- Cathode: Negative electrode; Anode: Positive electrode
- Electrolysis
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