Electrolysis Flashcards
Negative electrode
Cathode
Positive electrode
anode
Substance that conducts electricity
electrolyte
Why is a mixture of aluminium oxide plus cryolite used?
It saves energy, as the mixture has a lower boiling point
Why does aluminium oxide have to be molten for electrolysis to take place?
Aluminium oxide has to be separated from the ore, which contains other substances.
It enables ions to move to the electrodes.
What forms at the cathode and what forms at the anode for the electrolysis of aluminium?
-Aluminium forms at cathode
-Oxygen forms at anode
What are the half equations for the changes at each electrode in the electrolysis of molten aluminium oxide?
Cathode: Al^3+ + 3e– ⟶ Al
Anode: 2O^2- – 4e– ⟶ O2
Why are the carbon anodes regularly replaced?
Because they gradually burn away as the oxygen reacts with the hot carbon anodes, forming carbon dioxide gas
What is electrolysis?
The breaking down of ionic substances using electricity
What is formed at the cathode and anode on the electrolysis of molten lead bromide?
Cathode: lead (ions gain electrons)
Anode: bromine (ions lose electrons)
Half equations for lead and bromine
- Pb^2+ + 2e– ⟶ Pb
- 2Br^- – 2e– ⟶ Br2
Rules for discharge of ions in electrolysis
+ions: the least reactive is discharged
-ions: group 7 is always first, then OH-
—> OH- forms O2 gas
When OH- forms O2 gas, what is the half equation?
4OH- —> 2H2O + O2 + 4e-
