electrolysis of lead bromide and brine

STARTER: Tell the person next to you... Q1 Why does solid Copper chloride not conduct electricity?

Q2 Why does it conduct electricity when dissolved in water?

Q3 How else could you make copper chloride conduct electricity?

Q4 What are the correct names for the positive and negative electrodes?

Q5 In the experiment above what gas is being produced that can bleach damp litmus paper?

Q6 Which electrode is it being produced from?

Q7 Explain how you know.

GROUP ACTIVITY:Practising half equations

• Write the half equation to show the reaction at the cathode during the electrolysis of

a) Copper Chloride b) Lead Bromide (lead has a valency of +2) c) Sodium Chloride d) Aluminum Bromide

• Write the half equation to show the reaction at the anode during the electrolysis of

a) Copper Chloride b) Lead Bromide c) Sodium Oxide

Electrolysis of molten lead bromide

• Pb2+ + 2e- Pb (lead metal at the (-)cathode).2Br- - 2e- Br2 (bromine gas at the (+)anode).

• Lead ions gain electrons (reduction) to form lead atoms.

• Bromide ions lose electrons (oxidation) to form bromine atoms.

• The bromine atoms combine to form molecules of bromine gas.

• The overall reaction isPbBr2(l) Pb(s) + Br2(g)

Electrolysis of brine – NaCl (aq)

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Electrolysis of brine

• Hydrogen is produced at the cathode• Chlorine is produced at the anode• The solution remaining is sodium hydroxide

Electrolysis of brine

• Hydrogen is produced at the cathode• Chlorine is produced at the anode• The solution remaining is sodium hydroxide

Cathy’s Ankles (CatHy’s AnCl)

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Electrolysis of brine

• Cathode (-)2H+

(aq) + 2e- H2(g)

SODIUM IS NOT FORMED

The sodium ion is more stable than the hydrogen ion in water H2O H+ + OH-

• Anode (+)2Cl-

(aq) – 2e- Cl2(g)

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If the metal ion is ABOVE hydrogen in the reactivity series then HYDROGEN gas is ALWAYS given off at the cathode

If the metal ion is BELOW hydrogen in the reactivity series then that METAL will be collected at the cathode

Chemicals from salt

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1413°C

Copy and complete the table below for the following aqueous solutions

Solution Product at cathode Product at anode

Potassium iodide

Copper bromide

Calcium oxide

Silver iodide

Lead iodide

Copy and complete the table below for the following aqueous solutions

Solution Product at cathode Product at anode

Potassium iodide

Copper bromide

Calcium oxide

Silver iodide

Lead iodide

Hydrogen

Copper

Hydrogen

Silver

Lead Iodine

Iodine

Oxygen

Bromine

Iodine

Now complete your electrolysis review sheet!

Stand up sit down 1. One person names a topic.

2. All pupils write a key word to do with the topic on a piece of paper

3. The person who chose the topic has 30 seconds to name as many key words to do with the topic as they can.

4. If the word the pupil has written down is said they have to sit down.

5. The aim for the topic chooser is to get everyone to sit down.

6. The aim for the pupils writing down a word is to out fox the topic chooser with a relevant but obscure word.