IC S4 P1+2 – First hand investigation and analyse information from secondary sources to predict and explain different products of aqueous and molten NaCl Use this in conjunction with the worksheet!

Electrolysis of salt 3 Na+ ions move to the cathode but do not accept electrons. It is the hydrogen ions (from water) that gain electrons. As a result hydrogen gas is formed at the cathode.

H2O is more easily reduced than Na+ H2O(l) + e-  ½ H2(g) + OH-(aq) RED CAT Cathode H2O is more easily reduced than Na+ H2O(l) + e-  ½ H2(g) + OH-(aq) This means that H2(g) and OH- is formed at the negative cathode. Na+ is left behind. Na+ Cl- H O- H+ H O

2Cl- - + 2e- Cl2 Electrolysis of salt 1 Chlorine gas is formed At the ANODE. Why do you think that even though the reduction potentials predict that oxygen will be formed, we get chlorine? Standard Reduction Potentials (1M) Chlorine gas is formed 2Cl- - + 2e- Cl2

2Cl- - + 2e- Cl2 Electrolysis of salt 1 Chlorine gas is formed AN OX Anode Chloride and water have similar reduction potentials. But the NaCl is 2M concentration and in this condition it has a lower potential than water and is more easily oxidised. 2Cl-  Cl2 + 2e- Chlorine gas is formed 2Cl- - + 2e- Cl2

What happens to the various ions? Electrolysis of salt 4 What happens to the various ions? No change “Spectator ion” Na+ Cl- Changed into chlorine gas at anode H O- Changed into hydrogen gas at cathode H+ No change “Spectator ion”

Electrolysis of salt 5 Sodium hydroxide is what is left in the solution at the end of electrolysis Na+ Cl- H O- H+ Na+ H O- Cl H Solution Electrodes

Electrolysis of salt A drag and drop activity

Complete Q1-7 on the worksheet.

What happens if we dilute the concentration of NaCl?

What happens if we dilute the concentration of NaCl? RED CAT Cathode H2O is more easily reduced than Na+ H2O + e-  ½ H2 + OH- This means that H2(g) and OH- is formed at the negative cathode. Na+ is left behind.

What happens if we dilute the concentration of NaCl to 1.00 M? AN OX Anode Under Standard conditions H2O is more easily oxidised than Cl-. H2O +  2H+ + ½ O2 + 2e- This means that H+ and O2 is formed at the negative cathode.

Complete Q8 - 10.

What do you predict would happen if we could perform electrolysis on molten NaCl?

Molten NaCl. Contains only Na+ and Cl- ions. Anode (Oxidation) 2Cl- (l)  Cl2(g) + 2e- Cathode (Reduction) Na+(l) + e-  Na(l)

Uses of the products of electrolysis of NaCl(aq) Uses of the products of electrolysis of NaCl(aq). (You do not need to know all of this but it is interesting)

Electrolysis of salt - summary A drag and drop activity

Uses of chlorine 1 Sterilisation of water e.g. swimming pools and drinking water Sodium chloride ‘rock salt’ solution electrolysis Chlorine gas Bleaching agent, e.g. paper industry

Uses of chlorine 2 Sterilisation of water e.g. swimming pools and drinking water Sodium chloride ‘rock salt’ solution electrolysis Bleaching agent, e.g. paper industry Chlorine gas Manufacture of HCl continued Manufacture of Cl-containing organic chemicals

Uses of chlorine 3 Manufacture of PVC and Manufacture of HCl other plastics Manufacture of HCl

Uses of chlorine 4 Manufacture of PVC and Manufacture of HCl other plastics Manufacture of HCl Pesticides Manufacture of Cl-containing organic chemicals Solvents, e.g. solvent for tippex, & ‘dry cleaning’ dyes

Uses of sodium hydroxide 1 Extraction of aluminium Sodium chloride ‘rock salt’ solution Manufacture of soap electrolysis Sodium hydroxide Manufacture of Paper

Uses of sodium hydroxide 2 Extraction of aluminium Sodium chloride ‘rock salt’ solution Manufacture of soap Sodium hydroxide solution electrolysis Manufacture of Paper Textiles (wool, cotton)

Uses of sodium hydroxide 3 Extraction of aluminium Sodium chloride ‘rock salt’ solution Manufacture of soap Sodium hydroxide solution electrolysis Manufacture of Paper Textiles (wool, cotton) Neutralisation of acid effluents

Uses of Cl and NaOH A drag and drop activity

Uses of products from salt Join the appropriate substances with arrows. chlorine hydrogen Sodium hydroxide salt Hydrochloric acid pvc soap bleach Organic chlorides Aluminium extraction dyes Acid neutralisation

Purify Salt Water Why Purify? Mg2+ + Ca2+ + SO42- + Fe2+ +

Purify Salt Water Why Purify? Mg2+ + 2OH-  Mg(OH)2 Ca2+ + CO32-  CaCO3 SO42- + Ca2+  CaSO4 Fe2+ + 2OH-  Fe(OH)2

Net ionic equation? Ignore the spectator ion(s) 2H2O + 2Cl-  Cl2 + H2 + 2OH- Full equation? Include the spectator ion(s)

Net ionic equation? Ignore the spectator ion(s) 2H2O + 2Cl-  Cl2 + H2 + 2OH- Full equation? Include the spectator ion(s) 2H2O + 2NaCl  Cl2 + H2 + 2NaOH

Mercury Process Diaphragm Process Membrane Process Mercury process actually produes Na at the cahode… Na then reacts with water 2Na + H2O  2NaOH + H2