CC10a Electrolysis
- CC10b Products From Electrolysis
- CC11a Reactivity
- CC11b Ores
- CC11c Oxidation and Reduction
- CC11d Life Cycle Assessment and Recycling
- CC12a Dynamic Equilibrium
Positive ions (cations) migrate towards the cathode, while negative ions (anions) migrate towards the anode.
An electrolyte is a substance that dissociates in water into charged particles called ions. Positively charged ions are called cations
Oxidation is loss of electrons, gain of oxygen or loss of hydrogen. Reduction is gain of electrons, loss of oxygen or gain or hydrogen.
Electrolysis is the passing of a direct electric current through an electrolyte which is producing chemical reactions at the electrodes and decomposition of the materials
Balance the half equation for the formation of aluminium during electrolysis: Al3+ + e- → Al.
Common anode half-reactions (oxidation):
- Metal electrodes:
- Zn(s) → Zn²+(aq) + 2e-
- Cu(s) → Cu²+(aq) + 2e-
- Fe(s) → Fe²+(aq) + 2e-
- Aqueous solutions with halide ions:
- 2Cl-(aq) → Cl2(g) + 2e-
- 2Br-(aq) → Br2(l) + 2e-
- Water electrolysis:
- 2H2O(l) → O2(g) + 4H+(aq) + 4e-
Common cathode half-reactions (reduction):
- Metal ions in solution:
- Cu²+(aq) + 2e- → Cu(s)
- Zn²+(aq) + 2e- → Zn(s)
- Ag+(aq) + e- → Ag(s)
- Hydrogen ions in solution:
- 2H+(aq) + 2e- → H2(g)
To predict the products of electrolysis of molten ionic solids, identify the positive and negative ions present in the compound, then remember that the positive metal ions will be reduced to the metal at the cathode (negative electrode), while the negative non-metal ions will be oxidized to form the non-metal element at the anode (positive electrode)
To decide what substance is made at the cathode, we must use the reactivity series. Metal reactivity is compared to hydrogen. If the metal element formed during electrolysis is more reactive than hydrogen, then hydrogen will be produced at the cathode.
at the cathode (negative electrode), hydrogen gas is typically produced through the reduction of hydrogen ions (H+) from the solution, gaining electrons to form hydrogen molecules (H2), represented by the half-reaction: 2H+ + 2e- → H2
