Ch21_6 - Electrolysis of Aqueous NaOH Electrolysis of...

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Unformatted text preview: Electrolysis of Aqueous NaOH Electrolysis of Aqueous NaOH 1 2 Electrolysis Electrolysis of Molten NaCl Electrolysis of Molten NaCl Electric Energy ---> Chemical Change Electric Energy ---> Chemical Change Electric Energy ----> Chemical Change Eo Anode (+) = -0.40 V 4 OH- ---> O2(g) + 2 H2O + 2eCathode (-) Eo = -0.83 V 4 H2O + 4e- ---> 2 H 2 + 4 OHEo for cell = -1.23 V electrons Anode (+) Eo = -1.36 V 2 Cl- ---> Cl 2(g) + 2e- Electrolysis of molten NaCl. + Anode Cathode Cl- Na+ electrons Here a battery “pumps” electrons from Cl- to Na +. Cathode (-) BATTERY BATTERY 3 Na+ + e- ---> Na + Anode Cathode Cl- Na+ Eo = -2.71 V Eo for cell = -4.07 V External energy needed because Eo is (-). Note that signs of electrodes are reversed from batteries. Electrolysis of Aqueous NaCl Electrolysis of Aqueous NaCl Anode (+) Eo = -1.36 V 2 Cl- ---> Cl 2(g) + 2eCathode (-) Eo = -0.83 V 2 H2O + 2e- ---> H 2 + 2 OHEo for cell = -2.19 V Note that H 2O is more is easily reduced + +. than Na than 4 Electrolysis of Aqueous NaCl 5 Cells like these are the source of NaOH and Cl2. In 1995 25.1 x 10 9 lb Cl2 25.1 26.1 x 10 9 lb NaOH 26.1 electrons BATTERY Anode Also the source of NaOCl for use in bleach. Cathode Cl- Na+ H2O Page 1 Electrolysis of Aqueous CuCl2 Electrolysis of Aqueous CuCl2 Anode (+) Eo = -1.36 V 2 Cl- ---> Cl 2(g) + 2eCathode (-) Eo = +0.34 V Cu2+ + 2e- ---> Cu Eo for cell = -1.02 V Note that Cu is more Note + easily reduced than either H 2O or Na +. Anode either electrons BATTERY Cathode Cl- Cu2+ H2O 6 Producing Aluminum Producing Aluminum 7 2 Al2O3 + 3 C ---> 4 Al + 3 CO 2 Charles Hall (1863-1914) developed electrolysis process. Founded Alcoa. Page 2 ...
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