Topic 4: Electrochemistry
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Define electrolysis.
The decomposition of an ionic compound when molten or in aqueous solution, by the passage of an electric current.
What is formed in the cathode?
Metals or hydrogen
What is formed in the anode?
Non-metals (other than hydrogen)
What is an electrolyte?
A substance that conducts electricity when in the molten state or in solution.
How is electricity carried by the electrolyte?
By ions.
What are the electrodes made up of?
Unreactive metals.
Give an example of a material an electrode would be made up of.
graphite, platinum
What is the positive electrode?
The anode
What is the negative electrode?
The cathode
Describe the transfer of charge during electrolysis.
The transfer of charge is seen by: the movement of electrons in the metallic or graphite electrodes the loss or gain of electrons from the external circuit the movement of ions in the electrolyte
During the electrolysis of lead (II) bromide, what is produced in the cathode and anode?
At the cathode: Lead At the anode: Bromine
Write the word and symbol equation for the decomposition of molten lead(II) bromide.
molten lead (II) bromide —> bromine + lead PbBr2 (l) —> Br2 (g) + Pb (l)
Write the half-equation for what happened in the cathode during electrolysis of lead (II) bromide.
Pb2+ + 2e- —-> Pb
Write the half-equation for what happens in the anode during electrolysis of lead (II) bromide.
2Br- —> Br2 + e-