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Electrolysis of salt 3

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.

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Electrolysis of salt 3

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

  2. 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.

  3. Na+ Cl- H H H O O- 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. H+

  4. Electrolysis of salt 1 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

  5. Electrolysis of salt 1 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

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

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

  8. Electrolysis of salt

  9. Complete Q1-7 on the worksheet.

  10. What happens if we dilute the concentration of NaCl?

  11. 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.

  12. 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.

  13. Complete Q8 - 10.

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

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

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

  17. Electrolysis of salt - summary

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

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

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

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

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

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

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

  25. Uses of Cl and NaOH

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

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

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

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

  30. 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

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

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