4.3 Electrolysis Flashcards
(20 cards)
Electrolytes
Melted or dissolved ionic compounds in a solution.
Where do positive snd negatively charged ions go in electrolysis?
- Cations (positive ions) = cathode (negative electrode)
- Anions (negative ions) = anode (positive electrode)
What happens when ions move to electrodes?
They are discharged, producing elements.
Electrolysis
Splitting ionic compounds using electricity.
How do cations and anions move to electrodes?
Passing an electric current through electrolyte causes ions to move to opposite-charged electrodes.
Half equation for cations
Cations + electron(s) —> metal or hydrogen
Half equation for anions
Anions —> halide or oxygen + electron(s)
What is produced at the cathode in molten solution?
Metal
What is produced at the anode in molten solution?
Non-metal
Why is electrolysis used?
To extract a metal that is too reactive to be extracted by reduction with carbon or reacts with carbon.
Why is a mixture used as the electrolyte in aqueous electrolysis?
- Mixture means atoms of different sized
- This disrupts ionic lattice
- Lowers melting point
- Saves energy and money
Why is aqueous electrolysis expensive?
Large sums of energy used in extraction process, to melt compound and to produce electrical current.
What mixture is used in aqueous electrolysis?
Aluminium oxide and cryolite.
Why must the positive electrode be continually replaced?
- Made of graphite (unreactibe, cheap
- High temperatures make graphite react with oxygen.
- Overtime carbon react with oxygen to form carbon dioxide.
- Replaced.
When is hydrogen produced at the cathode?
If the metal is more reactive than hydrogen.
When is oxygen produced at the anode?
Anytime unless there is a halide in the solution, in which the halogen will be produced.
Why are there options in what is produced in aqueous electrolysis?
Water molecules break down into hydrogen ions and hydroxide ions that are discharged
Reaction at cathode
Reduction - cations gain electrons.
Reaction at anode
Oxidation - anion loses electrons
How can reactions at electrodes be represented?
Half equations.
