4.4.3 Electrolysis Flashcards
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 and what is an anode?
Cathode is the negative electrode, anode is the positive electrode
What occurs at the cathode and what occurs at the anode during electrolysis?
Reduction occurs at the cathode Oxidation occurs at the anode
In aqueous electrolysis, which element is discharged at the
cathode? Oxygen is produced at the anode unless what?
The less reactive element discharges at the cathode. Hydrogen is produced 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.
What are the half equations in the extraction of aluminium?
Al3+ + 3 e− → Al (cathode)
2 O2− → O2 + 4 e− (anode)
Oxygen reacts with C of the anode producing CO2.
Why is cryolite used in this process?
It lowers the melting point of aluminium oxide, reducing energy costs
What are the half equations in electrolysis of the aqueous Na2SO4?
2 H+ + 2 e− → H2 (cathode)
4 OH− → 2 H2O + O2 + 4 e− (anode)
What are the half equations in electrolysis of the molten and
aqueous KCl?
K+ + e− → K (cathode)
2 Cl− → Cl2 + 2 e− (anode)
2 H+ + 2 e− → H2 (cathode)
2 Cl− → Cl2 + 2 e− (anode), respectively
What are the half equations in electrolysis of the aqueous
CuBr2?
Cu2+ + 2 e− → Cu (cathode) 2 Br− → Br2 + 2 e− (anode)
