GCSE CHEMISTRY ELECTROLYSIS REVISION SUMMARY WITH EXAMPLES

C3 Topic 3 Electrolytic Processes
Recall ionic bonding
Non-Metal atoms react
Metal atoms react to get
to get full outer shells to
full outer shells to form
form ions.
ions.
They gain electrons to
They lose electrons to
form negative ions
form positive ions
(anions)
(cations)

Key idea
- Ions must be able to
move to carry an
- reverses this process using electricity to split up an ionic compound electric current
- melted (molten) or
dissolved in water
Easier Examples: molten substances – only 2 types of ions present (solution)
Electrolysis of molten sodium chloride


Cathode = negative electrode Anode – attracts anions

attracts cations Positive electrode
2Cl-  Cl2 + 2e-
2Na+ + 2e-  2Na
2Cl- Is Losing electrons

Na+ Is Gaining electrons This is called OXIDATION
OIL
This is called REDUCTION Na+
Cl- Cl-
RIG Na+

Heat NaCl (l) contains Na+ and Cl- ions
Same process:

Electrolysis of molten lead bromide
Cathode: Anode:
Pb2+ + 2e-  Pb (l) 2Br-  Br2 (g) + 2e-


Cathode = negative electrode
Anode – attracts anions
attracts cations
Positive electrode
Pb2+ Is Gaining electrons
REDUCTION
2Br- Is Losing electrons
RIG
This is called OXIDATION
Cl- Cl-
Pb2+ OIL


Heat – molten lead bromide