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Electrolysis

Electrolysis. non-spontaneous reaction is caused by the passage of an electric current through a solution. Electrolysis. Electrolysis of Sodium chloride (chlor-alkali process) molten reactants => liquid sodium and chlorine gas

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Electrolysis

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  1. Electrolysis • non-spontaneous reaction is caused by the passage of an electric current through a solution

  2. Electrolysis Electrolysis of Sodium chloride (chlor-alkali process) molten reactants => liquid sodium and chlorine gas aqueous reactants => caustic soda (sodium hydroxide) and chlorine gas

  3. Electrolysis Preparation of Aluminum (Hall process)

  4. Electrolytic Refining of Copper Cu(s) + Cu+2(aq) --> Cu+2(aq) + Cu(s) impure pure anode cathode impurities: anode mud; Ag, Au, Pb

  5. Quantitative Aspects of Electrolysis • 1 coulomb = 1 amp sec • 1 mole e- = 96,500 coulombs

  6. Electroplating EXAMPLE: How many grams of chromium can be plated from a Cr+6 solution in 45 minutes at a 25 amp current?

  7. Electroplating EXAMPLE: How many grams of chromium can be plated from a Cr+6 solution in 45 minutes at a 25 amp current? (45 min) #g Cr = ------------

  8. Electroplating EXAMPLE: How many grams of chromium can be plated from a Cr+6 solution in 45 minutes at a 25 amp current? definition of minute (45 min)(60 sec) #g Cr = --------------------- (1 min)

  9. Electroplating EXAMPLE: How many grams of chromium can be plated from a Cr+6 solution in 45 minutes at a 25 amp current? (45) (60 sec) (25 amp) #g Cr = --------------------------- (1)

  10. Electroplating EXAMPLE: How many grams of chromium can be plated from a Cr+6 solution in 45 minutes at a 25 amp current? definition of a coulomb (45)(60 sec)(25 amp)(1 C) #g Cr = ----------------------------- (1) (1 amp sec)

  11. Electroplating EXAMPLE: How many grams of chromium can be plated from a Cr+6 solution in 45 minutes at a 25 amp current? Faraday’s constant (45)(25)(60)(1 C)(1 mol e-) #g Cr = ---------------------------------- (1)(1)(96,500 C)

  12. Electroplating EXAMPLE: How many grams of chromium can be plated from a Cr+6 solution in 45 minutes at a 25 amp current? atomic weight (45)(60)(25)(1)(1 mol e-)(52 g Cr) #g Cr = ------------------------------------------- (1)(1)(96,500) (6 mol e-)

  13. Electroplating EXAMPLE: How many grams of chromium can be plated from a Cr+6 solution in 45 minutes at a 25 amp current? (45)(60)(25)(1)(1 mol e-)(52 g Cr) #g Cr = ------------------------------------------- (1)(1)(96,500)(6 mol e-) = 58 g Cr

  14. Corrosion O2(g) + 4 H+(aq) + 4 e- -----> 2 H2O(l) Eo = 1.23 V Rusting Fe(s) -----> Fe+2(aq) + 2 e- Eo = 0.44 V O2(g) + 4 H+(aq) + 4 e- -----> 2 H2O(l)Eo = 1.23 V ------------------------------------------- -------------- 2 Fe(s) + O2(g) + 4 H+(aq) -----> 2 H2O(l) + Fe+2(aq) Eo = 1.67 V

  15. Preventing Corrosion painting galvanizing sacrificial anode

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