5.5 Electrolysis Flashcards
What is electrolysis?
The breaking down of a compound using electricity
What is the positive electrode called?
Anode
What is the negative electrode called?
Cathode
What are electrodes made of?
A soiled which conducts electricity but is inert (unreactive), usually graphite or platinum
What is the electrolyte?
The substance to be broken down and it needs to conduct electricity
What are the only compounds which can conduct electricity?
Ionic compounds which are molten or dissolved so the ions are free to move
Why won’t solid ionic compounds work as electrolytes?
The ions can’t move
Why won’t covalent compounds work as electrolytes?
Molecules are not charged
What are the positive ions called and why?
Cations as they are attracted to the cathode
What are the negative ions called and why?
Anions as they are attracted to the anode
What does electrolysis of a molten ionic compound produce?
Its elements
What happens at the anode?
Non-metal ions lose electrons to form molecules (neutral)
What happens at the cathode?
Metal ions gain electrons to form atoms (neutral)
What can be seen when chloride undergoes molten electrolysis at the anode?
Bubbles of play green gas
What can be seen when magnesium undergoes molten electrolysis at the cathode?
Grey solid formed on surface of the cathode
What is it called when water molecules break apart to form H+ and OH- ions?
Dissociating
What happens during aqueous electrolysis to halide ions at the anode?
If present, that element is produced as normal
What happens during aqueous electrolysis when halide ions are not present at the anode?
O2 and H2O are produced according to the half equation:
4OH- —–> O2 + 2H2O + 4e-
What happens during aqueous electrolysis when the metal is less reactive than hydrogen at the cathode?
That element is produced as normal
What happens during aqueous electrolysis when the metal ion is more reactive than hydrogen at the cathode?
H2 is produced according to the half equation:
2H+ + 2e- —–> H2
What happens during aqueous electrolysis to the ions which did not reacts?
Remain leftover in the solution as the third product