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The electrochemical cell in electrolysis is termed an electrolytic

Electrolysis – Application of electrical current to produce a non-spontaneous redox reaction. The electrochemical cell in electrolysis is termed an electrolytic cell as compared to a voltaic or galvanic cell in which a

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The electrochemical cell in electrolysis is termed an electrolytic

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  1. Electrolysis – Application of electrical current to produce a non-spontaneous redox reaction. The electrochemical cell in electrolysis is termed an electrolytic cell as compared to a voltaic or galvanic cell in which a spontaneous reaction occurs. The voltage necessary to produce a non-spontaneous reaction must be greater than the value of Ecell for the competing spontaneous reaction.

  2. Example Problem:A zinc electrode immersed in 1 M zinc sulfate is connected to a copper electrode immersed in 1 M copper II sulfate. a) What are the relevant standard reduction potentials ? Cu 2+ + 2 e - Cu 0.34 V Zn 2+ + 2 e - Zn -0.76 V

  3. Example Problem:A zinc electrode immersed in 1 M zinc sulfate is connected to a copper electrode immersed in 1 M copper II sulfate. a) What are the expected spontaneous oxidation half reaction, reduction half reaction, and value of E  ? oxidation: Zn  Zn 2+ + 2 e - 0.76 V reduction: Cu 2+ + 2 e - Cu 0.34 V E  = 1.10 V

  4. Example Problem:A zinc electrode immersed in 1 M zinc sulfate is connected to a copper electrode immersed in 1 M copper II sulfate. a) What are the expected spontaneous oxidation half reaction, reduction half reaction, and value of Ecell for a comparable electrolytic cell? The non-spontaneous reaction is the reverse reaction. oxidation: Cu  Cu2+ + 2 e - - 0.34 V reduction: Zn 2+ + 2 e - Zn - 0.76 V Ecell - 1.10 V Voltage applied to the electrolytic cell must exceed 1.10 V

  5. Example Problem:A zinc electrode immersed in 1 M zinc sulfate is connected to a copper electrode immersed in 1 M copper II sulfate. a) Should the electrical current be applied to the zinc electrode or the copper electrode to produce an electrolytic cell ? Explain your answer. Electrical current consists of electrons, and electrons must be added to the desired cathode where reduction is to occur. This is the zinc electrode. oxidation: Cu  Cu2+ + 2 e - reduction: Zn 2+ + 2 e - Zn

  6. Example Problem 2: Two platinum electrodes are immersed in a 1 M solution of silver nitrate. An electrical current is applied to the electrode on the left to produce an electrolytic cell. a) What are the relevant standard reduction potentials ? Since nitrate is stable, only two possible reactants can be considered: Ag + and H2O. H2O has two possibilities Ag + + e - Ag 0.80 V 2 H2O + 2 e - H2 + 2 OH - - 0.83 V O2 + 4 H + + 2 e - 2 H2O 1.23 V

  7. Example Problem 2: Two platinum electrodes are immersed in a 1 M solution of silver nitrate. An electrical current is applied to the electrode on the left to produce an electrolytic cell. b) What are the expected spontaneous oxidation half reaction, reduction half reaction, and value of Ecell for the electrolytic cell given the relevant standard reduction potentials? Ag + + e - Ag 0.80 V 2H2O + 2 e - H2 + 2 OH - - 0.83 V O2 + 4 H + + 2 e - 2 H2O 1.23 V The reduction of Ag + will occur since no Ag is present for oxidation. H2O must therefore be oxidized. reduction: Ag + + e - Ag 0.80 V oxidation: 2 H2O  O2 + 4 H + + 2 e - - 1.23 V Ecell = -.43 V

  8. Example Problem 2: Two platinum electrodes are immersed in a 1 M solution of silver nitrate. An electrical current is applied to the electrode on the left to produce an electrolytic cell. c) How much voltage must be applied to produce silver metal? The voltage must exceed 2.03 V since the Ecell is – 2.03V reduction: Ag + + e - Ag 0.80 V oxidation: 2 H2O  O2 + 4 H + + 2 e - - 1.23 V Ecell = -.43 V

  9. Example Problem 2: Two platinum electrodes are immersed in a 1 M solution of silver nitrate. An electrical current is applied to the electrode on the left to produce an electrolytic cell. d) Will silver metal be deposited on the left electrode or the right electrode? Explain your answer. Left. The silver metal will be deposited on the cathode, the electrode receiving the electrical current.

  10. Example Problem 2: Two platinum electrodes are immersed in a 1 M solution of silver nitrate. An electrical current is applied to the electrode on the left to produce an electrolytic cell. e) What will be observed around the platinum electrode on the right? reduction: Ag + + e - Ag 0.80 V oxidation: 2 H2O  O2 + 4 H + + 2 e - - 1.23 V The right electrode is the anode where oxidation occurs. In this reaction, oxygen gas is formed by oxidation of water so bubbles of oxygen gas should be observed around the anode.

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