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IC S4 P1+2 – First hand investigation and analyse information from secondary sources to predict and explain different products of aqueous and molten NaCl.

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Presentation on theme: "IC S4 P1+2 – First hand investigation and analyse information from secondary sources to predict and explain different products of aqueous and molten NaCl."— Presentation transcript:

1 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!

2 Electrolysis of salt 3 do notNa + 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.

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4 RED CAT Cathode H 2 O is more easily reduced than Na + H 2 O(l) + e -  ½ H 2 (g)+ OH - (aq) This means that H 2 (g) and OH - is formed at the negative cathode. Na + is left behind. Na+ Cl- H H O H O- H+

5 Electrolysis of salt 1 Cl 2 2Cl e- 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)

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7 Electrolysis of salt 1 Cl 2 2Cl e- 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 -  Cl 2 + 2e -

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

10 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 H Solution Electrodes

11 Electrolysis of salt

12 Complete Q1-7 on the worksheet.

13 What happens if we dilute the concentration of NaCl?

14 RED CAT Cathode H 2 O is more easily reduced than Na + H 2 O + e -  ½ H 2 + OH - This means that H 2 (g) and OH - is formed at the negative cathode. Na + is left behind.

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

17 Complete Q

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

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

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

21 Electrolysis of salt - summary

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

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

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

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

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

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

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

29 Uses of Cl and NaOH

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

31 Salt Water Purify Why Purify? Mg 2++ Ca 2++ SO Fe 2++

32 Salt Water Purify Why Purify? Mg 2+ +2OH -  Mg(OH) 2 Ca 2++ CO 3 2-  CaCO 3 SO Ca 2+  CaSO 4 Fe 2++ 2OH -  Fe(OH) 2

33 Net ionic equation? Ignore the spectator ion(s) 2H 2 O+2Cl -  Cl 2 +H 2 + 2OH - Full equation? Include the spectator ion(s)

34 Net ionic equation? Ignore the spectator ion(s) 2H 2 O+2Cl -  Cl 2 +H 2 + 2OH - Full equation? Include the spectator ion(s) 2H 2 O+2NaCl  Cl 2 +H 2 + 2NaOH

35 Mercury ProcessDiaphragm ProcessMembrane Process Mercury process actually produes Na at the cahode… Na then reacts with water 2Na + H 2 O  2NaOH+ H 2


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