C3.4 Flashcards
What is electrolysis?
Process in which an electric current is passed through a compound, causing a chemical change
What are the 3 components you need for electrolysis to work?
1) an electrolyte - compound in kiwuidnstate or in solution which contains mobile ions and conducts electricity
2) two electrodes (cathode, anode) - made from a metal or graphite, which conducts electricity to the electrolyte
3) an electrical supply such as a power pack or battery
What is a binary ionic compound?
Contains just two elements
What does it mean for the ions to be discharged?
When ions become atoms or molecules at an electrode
What happens during electrolysis of molten compounds?
1) the cations are attracted to the cathode where they gain electrons and turn into their atoms
2) this metal can be seen to form at the cathode
3) this reaction is a reduction (gains electrons)
4) the anions are attracted to the anode where they lose electrons to from their atom
5) this reaction is an oxidation (loss of electrons)
6) the non-metal forms at anode
7) the electrons are produced at the anode to the cathode pumped by a battery through the wires in the circuit
8) the products of moltennbinary ionic compounds will always be the two elements present in the compound
What are inert electrodes?
Not changed during electrolysis
Made from unreactive metals
Can be used for electrolysis of many ionic compounds in their liquid or aqueous solution
What happens during electrolysis of aqueous solutions?
1) aqueous solution contains hydrogen ions and hydroxide ions along with the cations and anions from the ionic compound
2) at the cathode the ‘least reactive element’ is formed, if the metal is less reactive than hydrogen then it will be produced
4) at the anode oxygen is formed unless a halogen is present within the ionic compound
5) that will be formed at the anode, always a non-metal
What is electroplating?
Type of electrolysis that uses non-inert electrodes (change during electrolysis)
Cathode - object you want to coat
Anode - piece of metal you want to coat the object with
Electrolyte - the solution containing ions of the coating metal
If trying to coat a silver piece of jewellery:
Cathode - piece of jewellery
Anode - piece of silver
Electrolyte - Silver nitrate solution
How does electroplating work?
1) metal ions from the electrolyte are discharged on the surface of the cathode (the object)
2) ions are replaced by metal ions leaving the surface of the anode
3) metal leaves the anode and is deposited on the object
4) process continues until the anode is used up
How is copper purified?
LOOK AT UR BOOK
Similar way to electroplating, but bothplates are copper
Cathode is very pure copper
Anode is impure copper
Copper sulfate used as electrolyte
1) cathode gains copper atoms and increases in mass while the anode loses copper atoms and decreases in mass
2) impurities from the anode fall off and collect underneath it
