Electrolytic Cells & Electrolysis Flashcards
Do electrolytic cells usually undergo a spontaneous or non-spontaneous reaction?
Non-spontaneous
Where does oxidation and reduction occur in electrolytic cells?
Oxidation occurs at the anode and reduction occurs at the cathode
What is an electrolytic cell made up of?
Two electrodes connected to a DC power supply and immersed in an electrolyte (solution/liquid that conducts electricity - contains freely moving ions)
Which is positive and negative electrode out of the anode and cathode?
Anode = positive electrode Cathode = negative electrode
What happens when the current is on in electrolytic cells?
The anions (negative ions) in the electrolyte move towards the anode, where oxidation occurs. The cations (positive ions) move towards the cathode, where reduction occurs. The oxidation and reduction reactions occur on the surface of the electrodes. Electrodes are often inert solids (eg, graphite and platinum) and are not involved in the electrolysis reaction.
How do you calculate E°?
E°cell = E°red - E°oxid
How do oxidation numbers allow you to determine which is the oxidant and reductant?
If the oxidation number increases, an atom is oxidised (reducing agent) and if the oxidation number decreases an atom is reduced (oxidising agent).
What happens if the electrolyte is an aqueous solution?
It is possible that the water will undergo oxidation (producing oxygen gas) or reduction (producing hydrogen gas).
Sum up an electrolytic cell
- Reverse of an electrochemical cell
- 1 cell with both electrodes dipping in electrolyte (conducting solution)
- Anode is positive (site of discharge of anions) and cathode is negative (site of discharge of cations)
- Has an external power supply (can’t work without it)
- To allow it to be spontaneous you can a) reverse the oxidant and reductant or b) use external power to force electron loss and gain
