Electrolysis
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What is electrolysis?
When an electrical current is used to break down compounds containing ions into their separate elements.
What is the substance being broken down called?
An electrolyte.
What are electrodes?
The solids that conduct electricity.
Negatively charged ions go to the _______ Positively charged ions go to the _______
Anode Cathode
What are cations and anions?
Cations are positive ions. Anions are negative ions.
Oxidation is ___________
loss of electrons.
Reduction is __________
gain of electrons.
In the electrolysis of lead bromide, what happens to the bromine ions?
They lose electrons, therefore they are oxidised.
What is the half equation for bromine in the electrolysis of lead bromide?
2Br- -> Br2 +2e-
What does a half equation involving reduction look like?
N+ +e- -> N
What does a half equation involving oxidation look like?
N- -> N + e-
What metals are extracted from their ores by electrolysis?
Metals more reactive than carbon.
Why is electrolysis an expensive process?
Electrolysis requires a lot of heat and electrical energy.
What does cryolite do to incur cheaper fuel costs?
It lowers the melting point of the compound so less energy is needed. Leading to cheaper fuel costs.
Why does the anode need constant replacement?
Oxygen gas forms at the anode and reacts with the carbon. Forming carbon dioxide. This wears away the anode.
What are aqueous solutions?
Ionic compounds dissolved in water.
Water molecules break down to form the ions: ____and ____.
OH- H+
What are halides?
Chemical compounds containing halogens.
PRACTICAL What should you do for hazards and risks when electrolysing aqueous solutions?
Use a low voltage to prevent electric shock.
How is oxygen gas produced in electrolysis of an aqueous solution? ___________________ break down to form __________. Which are attracted to the __________ and then _____________ to form oxygen atoms.
Water molecules OH- ions anode oxidised