Electrolysis Flashcards
What is electrolysis?
When ionic substances are separated into its elements using electricity.
What is an electrolyte?
An aqueous or liquid version of an ionic compound.
Why should the ionic compounds be in a liquid or aqueous state?
In solids, the ions aren’t free to move due to their strong electrostatic forces, disabling the ions from moving to the different electrodes. Melting or dissolving these compounds enable the ions to move around and separate.
What is the cathode?
The negatively charged electrode that gives electrons away. Where reduction takes place.
What is the anode?
The positively charged electrode that takes electrons away, Where oxidation occurs.
Why are electrodes made of graphite?
So that the electrons don’t react with electrolytes or the products formed, graphite is made of many carbon atoms bonded together which means that they are unreactive.
It has a very high melting point and is very unreactive but conductive.
Why is electrolysis with ionic solutions harder than with molten ionic compounds?
Because water will also form ions so its harder to predict what will be formed.
In an ionic solution, if the metal is less reactive than hydrogen what element would form at the cathode?
The metal.
In electrolysis with ionic solutions what other ions do we have to consider?
H+ ions and OH- ions
Why is aluminium expensive?
Because it takes lots of energy to undergo electrolysis as Aluminium has a very high melting point.
Describe displacement:
A more reactive metal will displace and less reactive metal from a compound.
How can carbon be used to extract metals?
It can displace a metal which is less reactive than it, producing the metal you want and CO2 as a waste product.
Why can’t carbon be used to extract aluminium?
Aluminium is more reactive than carbon so carbon cannot displace it. So electrolysis is required.
Explain the extraction process of aluminium:
-Aluminium oxide is purified
-Cryolite (an ionic compound with a lower melting point) is added to the aluminium oxide, to lower the melting point making it molten and able to go under electrolysis whilst requiring less money and energy.
-Electrolysis occurs, where the aluminium ions are attracted to the cathode, gaining electrons as they under go reduction. It falls as molten aluminium to the bottom where it is collected.
-Oxygen is oxidised as it gains electrons at the anode,
