Lead Bromide Electrolysis - Interactive Simulation

Ready

🔥 Heating to 370°C (molten)

⏱️ 00:00

Show ions

Show equations

Show Br₂ bubbles

Heat effects

⚠️ TOXIC Br₂: use fume hood

DC Source

Anode (+) Graphite

Cathode (−) Steel/Graphite

⚗️ Equations (Molten PbBr₂) Write these in ICSE answers

Ionisation: PbBr₂ (molten) → Pb²⁺ + 2Br⁻

Cathode (−) reduction: Pb²⁺ + 2e⁻ → Pb (lead metal)

Anode (+) oxidation: 2Br⁻ → Br₂ + 2e⁻ (bromine gas)

Overall: PbBr₂ (molten) → Pb (s) + Br₂ (g)

Teacher’s Demonstration Guide (Expanded)

Mobile-friendly notes + viva + recap for Lead Bromide electrolysis

🔬 Why PbBr₂ must be molten

PbBr₂ is ionic. It conducts electricity only when its ions are free to move. In solid PbBr₂, ions are locked in a crystal lattice → no conduction. Heating to ~370°C+ melts the salt and the ions become mobile → conduction starts.

Exam line: “Molten PbBr₂ conducts because ions are free to move; solid does not.”

⚡ Ion migration (what to say)

Pb²⁺ (cation) migrates to the cathode (−) and gains electrons (reduction).

Br⁻ (anion) migrates to the anode (+) and loses electrons (oxidation).

Use OIL RIG: Oxidation Is Loss; Reduction Is Gain (of electrons).

👀 Observations checklist (ICSE-ready)

Cathode Silvery-grey lead metal forms (deposit/collection at bottom).

Anode Reddish-brown bromine gas evolves (pungent, toxic).

Colour Br₂: reddish-brown; Pb: grey/silvery.

🧪 Quick recap table (2× clarity)

Part	What happens	Equation
Electrolyte	Molten PbBr₂ gives free ions	PbBr₂ → Pb²⁺ + 2Br⁻
Cathode (−)	Pb²⁺ gains e⁻ → lead metal	Pb²⁺ + 2e⁻ → Pb
Anode (+)	Br⁻ loses e⁻ → bromine gas	2Br⁻ → Br₂ + 2e⁻
Overall	Salt splits into metal + halogen	PbBr₂ → Pb + Br₂

⚠️ Safety (expanded)

Bromine gas is toxic and corrosive → always use a fume hood.
Molten salt is ~370°C+ → burn hazard; heat-resistant gloves + goggles.
Do not inhale fumes; keep neutralising/ventilation protocols ready in real labs.

🎯 Common mistakes students make

Forgetting to write “molten” (most common ICSE marking point).
Mixing up electrodes: cation → cathode, anion → anode.
Writing Br⁻ discharge at cathode (wrong): Br⁻ is oxidised at the anode.
Missing electrons in half equations.

🗣️ Viva / Oral Questions (with answers)

Why is PbBr₂ heated?
To melt it so ions are free to move and conduct.
Name the products.
Lead at cathode, bromine at anode.
Which electrode is oxidation?
Anode: 2Br⁻ → Br₂ + 2e⁻.
Which electrode is reduction?
Cathode: Pb²⁺ + 2e⁻ → Pb.
What happens if PbBr₂ is solid?
No electrolysis because ions cannot move.

📝 Mini-quiz (quick self-check)

Q1. Which ion goes to cathode? (Answer: Pb²⁺)

Q2. Write the anode half-equation. (Answer: 2Br⁻ → Br₂ + 2e⁻)

Q3. What is the colour of bromine gas? (Answer: reddish-brown)

📜 Expanded step-by-step teaching script

Hook: “Solid ionic compounds don’t conduct—but molten ones do. Let’s see why.”
Point out parts: DC source, electrodes, molten electrolyte, anode(+), cathode(−).
Safety: “Bromine gas is toxic—use fume hood in real lab.”
Start: Tap Start and ask: “Which ions move where?”
Cathode: Highlight reduction; write Pb²⁺ + 2e⁻ → Pb.
Anode: Highlight oxidation; write 2Br⁻ → Br₂ + 2e⁻.
Observation: “Grey Pb forms; reddish-brown Br₂ gas evolves.”
Check: Ask students to state OIL RIG and identify oxidation/reduction.
Exit ticket: “Why must it be molten?” (Key marking point.)