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Chemical rxns can produce electricity = galvanic (voltaic) cell OR

Topic: Electrolytic Cell Do now: p.19 in packet, cross out # 19 and do # 20 and #21. must label anode/cathode . Chemical rxns can produce electricity = galvanic (voltaic) cell OR Electrical energy used to carry out chemical reactions = electrolytic cell .

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Chemical rxns can produce electricity = galvanic (voltaic) cell OR

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  1. Topic: Electrolytic CellDo now: p.19 in packet, cross out # 19 and do # 20 and #21. must label anode/cathode 

  2. Chemical rxns can produce electricity = galvanic (voltaic) cell OR • Electrical energy used to carry out chemical reactions = electrolytic cell Electrolytic Cell need electrical energy so NONSPONTANEOUS

  3. Galvanic Cell Chemical Potential Energy Electrical Potential Energy Electrolytic Cell Galvanic cell is a battery Electrolytic cell needs a battery

  4. Electrolytic Cells • Nonspontaneous • Need battery or power supply • Consumes energy = endothermic

  5. What’s the difference? Battery in one. Electrons in galvanic flowing from – to + Electrons in electrylic flowing from + to - e-  e-  e- anode catode Electrolytic Cell a Fat Red Cat ate an Ox Use Table J, but opposite More active metal = cathode = negative Less active metal = anode = positive Galvanic Cell A Fat Red Cat ate an Ox Use Table J More active metal = anode = negative Less active metal = cathode = positive

  6. NONSPONTANEOUS e- flow Anode to Cathode But from + to – (opposite then we’d think) That’s why we use the battery SPONTANEOUS e- flow Anode to Cathode from – to + (just like we’d think) That’s why it’s spontaneous  e- e-  e-

  7. A POX on Electrolytic Cells • Anode – Positive – Oxidation A pox = a disease And electrolytic cell behave differently like they are diseased?!

  8. Various types of electrolytic cells • Fused Salt Cells – used to purify metals (Fused means melted = molten salt cell) • Add NaCl (s) and melt it • Now NaCl (l) • Why melt it?! • Why add CaCl2(s)??! • Na+1 is reduce to Na(l) • Na(l) is less dense then NaCl(l) so it floats on top • 20,000 tons of Na are produce this way in the US every year Molten b/c need ions Lowers MP – don’t need as much heat

  9. Fused Salt Cell (Molten salt cell) + - e- e- e- e- Gain electron So reduced So cathode Na+ Cl- Na+ Cl- lose electron So oxidized So anode (l) 2 Cl-+  Cl + 1 e- 2 Na+ + 1e- Na 2 BUT WAIT SOMETHING IS WRONG WITH OUR ANODE

  10. Various types of electrolytic cells 2. Electroplating A layer of a second metal is deposited on the metal electrode that acts as the cathode • Used to enhance the appearance of metal objects and protect them from corrosion.

  11. Various types of electrolytic cells 2. Electroplating • cathode = object to be plated • anode - made of metal want to plate on object • solution: contains ions of plating metal

  12. + - lose electron So oxidized So anode e- e- e- e- Ag  Ag+ + 1e- Gain electron So reduced So cathode NO3- Ag+ + 1e- Ag NO3-

  13. 3. Electrolysis of H2O H2 is produced at one electrode, O2 at the other. 2H2O + energy 2H2 + O2 Can you tell from the picture which electrode is producing H2?

  14. What do every one of these have in common?

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