C6 Flashcards
Electrolysis
Splitting of an ionic compound into elements using electricity
Electrolysis can only happen when…
Ions in the compound are free to move, so the compound must be in liquid or dissolved in a solvent- called the electrolyte
Why should electrodes be made from something like graphite or platinum?
They are inert so will not react
Positive metal ions move to
The negative electrode (cathode)
Negative non metal ions move to
Positive electrode (anode)
Negative electrode–
2H+ + 2e- –>
H2
Positive electrode–
2Cl- –>
Cl2 + 2e-
T/f? Electrolysis is expensive?
True
What metals is electrolysis used for?
Metals more reactive than carbon
If a compound is dissolved in water there’ll be 4 ions present:
- metal
- non metal
- hydrogen ions
- hydroxide ions
At the negative electrode, what is formed?
– if metal in the compound is less reactive than hydrogen, the metal will be formed
– if the metal is more reactive than hydrogen, hydrogen is formed
At the positive electrode, what is formed?
– if the compound contains a halogen, the halogen gas is formed
– if the compound doesn’t contain a halogen, oxygen is formed
Sodium chloride solution is electrolysed to produce…
Hydrogen gas, chlorine gas, sodium hydroxide solution
In sodium chloride solution, what do the ions move to?
- both positive ions move to the negative electrode
- less reactive hydrogen is discharged from negative electrode
- both negative ions move to the positive electrode
- halogen - chlorine - discharged
Where is aluminium extracted from?
A molten mixture of aluminium oxide and cryolite
Aluminium oxide is made from…
Bauxite - its ore
Why is cryolite added to aluminium oxide?
To lower the melting poin, so less energy is needed to melt it
Why must electrodes continually be replaced?
Hot gas reacts with carbon electrodes, burning them away and forming carbon dioxide
