C4 - Electrolysis Flashcards
(13 cards)
What is electrolysis?
Using direct current to split an ionic compound back to its element.
What is a disadvantage of electrolysis?
Expensive as uses a lot of energy.
What are the electrodes made of?
Graphite because they are unreactive ( inert) and conducts (delocalised electron).
Electrolysis required practical. Investigates the products made when solution changed.
- Repeat using different solutions
- Controls = volume and concentration of solutions, voltage and temperature.
- Independent = solutions used
- Dependent = products made at electrode.
- Cathode = copper is product then orange metal is visible, if hydrogen is then it fizzes and lit spill pops.
- Anode = if chlorine is product then it fizzes and damp blue litmus paper turns white, if oxygen is present then it fizzes and relights a glowing spill.
What does solution electrolysis mean? What happens to ions and H2O?
Ionic compound dissolved in water = aqueous.
Ions can move.
H2O splits into H+ and OH- ions.
What 4 ions does solution electrolysis produce?
H+ and OH- from H2O
M+ and NM- from ionic compound.
What can only be discharged at electrodes?
Only 2 ions out of the 4
What are the rules at the anode?
- If group 7 element present then it is made eg. Chlorine
- If not, OH- from water make O2.
What are the rules at the cathode?
- Metal is made if it is less reactive than hydrogen - mainly just copper
- If metal more reactive, then H+ from water makes hydrogen, H2.
What makes the solution become acidic?
If copper and oxygen are made then the H+ remains in solution which becomes acidic.
What makes the solution become alkaline?
If hydrogen and group 7 element are made then OH- remain in solution which becomes alkaline.
What is molten electrolysis? What does molten mean?
Compound split back to elements.
Ions are free to move.
Reverses ion formation.
Molten = melted to liquid
