Electrolysis - 5.4
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Why do covalent compounds not conduct electricity?
molecules are not charged
Why do ionic compounds only conduct electricity when molten or in solution?
so the ions are free to move
What is electrolysis?
the breaking down of a compound using electricity
What does the term cation refer to?
positive ions
What does the term anion refer to?
negative ions
what happens at the anode during electrolysis of a molten ionic compound
non-metal ions lose electrons to form molecules
what happens at the cathode during electrolysis of a molten ionic compound?
metal ions gain electrons to form (neutral) atoms
What is the positive electrode called?
anode
What is the negative electrode called?
cathode
What type of solid must electrodes be made from?
a solid that conducts electricity but is inert (unreactive) usually: graphite (cheap) or platinum (expensive)
What is meant by the term electrolyte?
the substance to be broken down into elements by an electric current needs to conduct electricity
What happens to the ions in water during electrolysis of aqueous compounds?
water molecules can break apart to form H+ and OH- ions
What happens at the anode during electrolysis of aqueous compounds?
If a halide in is present, that element is produced as per normal Otherwise, O2 and H2O are produced according to the half-equation
What is the half-equation used when O2 and H2O are produced at the anode?
4OH− → O2 + 2H2O + 4e−
What happens at the cathode during electrolysis of aqueous compounds?
If the metal is less reactive than hydrogen, that element is produced as per normal Otherwise, H2 is produced according to the half-equation
What is the half equation for when H2 is produced at the cathode during electrolysis of aqueous compounds?
2H+ + 2e− → H2
What happens to the ions that do not react during electrolysis of aqueous compounds?
Whichever ions did not react remain leftover in the solution as a third product
What is the balanced half equation for oxygen at the anode?
2O2- –> O2 +4e-
Explain why the positive electrode must be continually replaced
the electrode reacts with oxygen the electrode is graphite so carbon dioxide is produced