What is electrolysis?
The passing of an electric current through ionic substances that are molten or in solution to break them down into elements; ions are discharged (they lose/gain electrons) at electrodes to produce these
What is an electrolyte?
The liquid/solution which conducts electricity
What is a cathode?
A negative electrode
What is an anode?
A positive electrode
What occurs at the cathode?
Reduction & positive ions move towards it
What occurs at the anode?
Oxidation & negative ions move towards it
In aqueous electrolysis, which element is discharged at the cathode and anode?
The less reactive element discharges at the cathode. Hydrogen is produced (at the cathode) unless there is a less reactive metal, in which case the said metal is produced. Oxygen is produced at the anode unless the solution contains halide ions, in which case halogen molecules are produced.
How is aluminium manufactured? Why is it expensive?
Aluminium is made through the electrolysis of aluminium oxide and cryolite.
Lots of energy is needed to produce the current in electrolysis which makes this process expensive.
When is electrolysis used to extract metals?
When the metal is more reactive than carbon
What are the half equations in the extraction of aluminium?
Al3+ + 3 e- → Al (cathode)
2O2- → O2+4e- (anode)
Oxygen reacts with C of the anode producing CO,
Why is cryolite used in manufacturing of aluminium?
It lowers the melting point of aluminium oxide, reducing energy costs
In a molten compound electrolysis, which element is discharged at the cathode and anode?
The metal is produced at the cathode. The non metals are produced at the anode
What is a the electrode made of
Carbon
If a solution has pH 6, how much more acidic is it than pH 7?
10× more acidic.
If a solution has pH 5, how much more acidic is it than pH 7?
100× more acidic.
If a solution has pH 9, how much more basic is it than pH 7?
100× more basic.
In electrolysis whats the bottom part of it
Molten metal
What is a chemical cell
Chemical cell:
Produces electricity from a spontaneous chemical reaction.
No external power is needed; the reaction happens naturally.
Electrons flow through a circuit from one electrode to another, generating electric current.
What is the main difference between a chemical cell and electrolysis
Key difference:
Electrolysis uses electricity to cause a reaction, whereas a chemical cell produces electricity from a reaction.
Some of the copper produced did not stick to the negative electrode but fell to the
bottom of the beaker.
Suggest how the students could find the total mass of copper produced.
1Remove the negative electrode and weigh it to find the mass of copper deposited on it.
2Filter the solution to collect copper particles that fell to the bottom of the beaker.
3Wash and dry the collected copper to remove any acid or solution.
4Weigh the collected copper and add this to the mass on the electrode to find the total mass of copper produced.
