C6 - Electrolysis Flashcards
What is electrolysis?
Splitting up substances using electricity
Must be ionic, not covalent
Electric current is used to breakdown a substance made up of ions
What is an electrolyte?
Name for the substance being broken down
Electrolyte has to contain free moving ions - usually molten/dissolved ionic substance
Free ions conduct the electricity
How electrolysis works
Based on an electrical circuit that includes an electrolyte and two electrodes
Graphite - only 3 carbon bonds - fourth electron delocalises
The electrodes are placed into the electrolyte and ions move from one electrode to the other - this allows the conduction of electricity through the circuit
PANIC acronym
Positive anode negative is cathode
Negative ions…
Attract to anode
Positive ions…
Attract to the cathode
Binary substances
One negative and one positive ion
Electrolysis of solutions
H2O -> H+ + OH-
Water disassociates into ions
Metals from positive ions - competition to which gets to the cathode, other is left (depending on how reactive)
Less reactive gives up ionic status and goes to the cathode
Rules of electrolysis
At the cathode, the less reactive element is formed (metal vs hydrogen)
If the metal is more reactive, hydrogen gas forms
If metal is less reactive, metal forms
At the anode - if a halogen is present (F, Cl, Br, I) then form (will be discharged at the anode)
If no halogen, oxygen is given off (from OH ions)
Uses of aluminium
Cooking foil
Power cables
Cars
Aeroplanes
Reflective, light, don’t rust
Aluminium ore
Bauxite
Mined in Russia and Jamaica
Purify the bauxite to make aluminium oxide
Cannot he extracted in a blast furnace - need electrolysis
Electrolysis of aluminium oxide
Mix with cryalite to reduce MP from 2050 degrees to 850 degrees
Tank for aluminium electrolysis
• steel case
• graphite cathode/anode
• molten aluminium
