Predict the identity of the products at each electrode for the electrolysis of a binary compound in the molten state

What is Electrolysis?

Think of electrolysis as a power‑driven factory that splits a substance into its parts using electricity. ⚡ In a molten state, ions are free to move, just like cars on an open highway.

Key Players: Anode & Cathode

• Anode (positive electrode) – where oxidation happens (loss of electrons).
• Cathode (negative electrode) – where reduction happens (gain of electrons).

Remember the rule: Electrons flow from the anode to the cathode. 🔋

Predicting Products – The “Rule of Thumb”

1. Write the ionic form of the molten compound.
2. Identify which ions are more likely to give up or gain electrons.
3. Apply the standard reduction potentials (remember the electrochemical series).
4. Match the ions to the electrodes: cations → cathode, anions → anode.

⚠️ Tip: If the metal cation is less electronegative than the halide anion, the metal usually goes to the cathode.

Example 1 – Molten NaCl

Molten sodium chloride dissociates into \$Na^+\$ and \$Cl^-\$ ions.

Result: Na metal at the cathode and Cl₂ gas at the anode. 🔬

Example 2 – Molten CuCl₂

Molten copper(II) chloride gives \$Cu^{2+}\$ and \$Cl^-\$ ions.

Result: Cu metal at the cathode and Cl₂ gas at the anode.

Exam Tip Box

• Always write the ionic equations first.
• Use the electrochemical series to decide which ion is oxidised/reduced.
• Remember: Metal cations → cathode, Halide anions → anode (unless you’re dealing with a non‑halide anion).
• Check the charge balance – the total charge on each side of the equation must match.
• Practice with different molten salts to build confidence.

Quick Reference Table – Common Molten Salts

Use this table as a quick mental checklist before you write your answer. 📚