5.5 - Electrolysis Flashcards
What is the charge of the anode?
Positive
What is the charge of the cathode?
Negative
What ion is attracted to the anode?
Anions
What ion is attracted to the cathode?
Cations
What is the electrolyte?
The substance to be broken down is called the electrolyte,
What state do ionic compounds need to be in for electrolysis to work?
Molten or aqueous.
What does molten electrolysis produce?
Compound → Elements
What happens at the anode in molten electrolysis?
Non-metal ions lose electrons to form molecules.
What happens at the cathode in molten electrolysis?
Metal ions gain electrons to form atoms.
Example of molten electrolysis?
Lead Bromide
What happens to PbBr in molten electrolysis?
Pb has a charge of 2+ so it needs to gain two electrons - therefore it is attracted to the cathode.
Br has a charge of 1- so it need to gain an electron. However bromine is diatomic, we need to keep this in mind when forming are half equations.
What happens to ions in water?
Water molecules can break apart (dissociate) to form H+ and OH- ions.
What rules are there at the anode for aqueous electrolysis?
- If a halide ion (Cl−/Br−/I−) is present, that element is produced.
- Otherwise, O2 and H2O are produced according to the following half-equation:
4OH− → O2 + 2H2O + 4e−
What rules are there at the cathode for aqueous electrolysis?
- If the metal is less reactive than hydrogen, that element is produced.
- Otherwise, H2 is produced according to the following half-equation:
2H+ + 2e− → H2
What happens to the ions that don’t react in aqueous electrolysis?
Whichever ions did not react remain leftover in the solution as a third product.
