Electrolysis Flashcards
What is electrolysis?
The breakdown of a molten or aqueous ionic compound by passing electricity through it.
What are electrodes?
The conducting rods
What are electrolytes?
The molten or aqueous ionic compound which is broken down via electricity
How to metals conduct electricity?
They have free delocalised electrons which can move and carry a charge.
How do ionic compounds conduct electricity?
They must be liquid (molten or aqueous) so the ions are free to move around and carry a charge.
What are the units for energy?
Joules
What is the positive electrode called?
Anode
What is the negative electrode called?
Cathode
What are electrodes made of?
Graphite
Why is the electrolyte heated?
So it is molten and has free ions to carry a charge
What ions move to to the anode and cathode in electrolysis?
E.g. Molten Lithium Chloride
Positive ions move to the cathode
Negative ions move to the anode
Lithium is formed at the cathode
Anode is formed at the chlorine
What are the observations for the decomposition of lithium chloride via electrolysis and half equations?
Cathode: Li+(aq) + e- —> Li (s)
Observations: Grey Solid
Anode: Cl-(aq) —> Cl2(g) + 2e-
Observations: Yellow-green gas
What are the observations for the decomposition of molten lead bromide via electrolysis and half equations?
Cathode: Pb2+(aq) + 2e- —> Pb (s)
Observations: Grey Solid
Anode: br-(aq) —> br2 (g) + 2e-
Observations: red-brown gas
What is aluminium ore?
Bauxite
Why is molten cryolite used in the extraction of aluminium from bauxite?
It lowers the melting point of the alumina
Reduces the operating temperature
Increases conductivity
Why do the electrodes have to be replaced in the extraction of aluminium?
They react with the oxygen produced to produce carbon dioxide and wear away.
Why is it better to recycle aluminium then extract it from bauxite?
Reduces waste
Reduces cost as electrolysis requires a lot of heat energy
What are the observations for the decomposition of aluminium from bauxite via electrolysis and half equations?
Cathode: Al3+(aq) + 3e- —> Al(s)
Observations: Grey solid
Anode: 2O2- (aq) —> O2 (g) + 4e-
Observations: colourless gas, bubbles
How is sulfuric acid solution split up by electrolysis? Include Half equations and observations
Cathode: H+ ions which create H atoms which combine to H2
2H+ (aq) + 2e- —> H2 (g)
Observations - colourless gas, bubbles
Anode: OH- & SO4 2- ions which create O Atoms which combine to form O2
4OH-(aq) —> O2 (g) + 2H2O (I) + 4e-
Observations - colourless gas, bubbles
