Molten Ionic compounds
Question 1 – ions formed by molten ionic compounds - Using Periodic Table
Name
Formula
Sodium Chloride
Lead Bromide
Potassium Iodide
Aluminium Oxide
Lead Chloride
NaCl
PbBr2
KI
Al2O3
PbCl2
Positive ions
formed (cations)
Negative ions
formed (anions)
Pb2+
Br-
Al3+
Question 2: Give the half equation for the following
Worked examples: Lead Bromide PbBr2
At the cathode: You know that the Lead is a positive metal ion and will be discharged at the
negative electrode. Here it will pick up electrons to turn from a positively charged ion to an
atom without a charge.
Pb2+ + electron → Pb
This is non balanced as lead has a positive charge of 2 and each electron has a
negative charge of 1.
Pb2+ + 2 electrons → Pb
You need two electrons to balance the charge.
At the Anode: You know that the Bromine is a negative non-metal ion and will be discharged
at the positive electrode. Here it will get rid of an electron to turn from a negatively charged
ion to an atom without a charge.
Br- → Br + electron
This is balanced looks balanced but isn’t yet as Bromine will only form as the
molecule Br2. Oxygen, nitrogen and all the halogens like to form these diatomic
gases (2 atom gases)
Br- → Br2 + electron
So, you have to balance it again for atoms and electrons
2Br- → Br2 + 2 electrons
Lead Chloride
At the cathode
Pb2+ +
Sodium chloride
Na+
Potassium Iodide
→ Pb
+
→
+
→
At the anode
Cl- →
Cl-
Cl2 +
→
+
→
+
Molten Ionic compounds
Question 3: Oxidation and reduction
Remember Oil Rig
Oxidation is Loss (of electrons)
Reduction is Gain (of electrons)
State what has happened at each electrode Oxidation or reduction.
At the cathode
Lead Chloride
Sodium chloride
Potassium Iodide
At the anode