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I understand that when you are finding the cathode of a voltaic (spontaneous) cell, you chose the substance with the half reaction that has the highest redox potential. With an electrolytic cell wouldn't it be the opposite since you are pushing electrons the opposite direction from what is spontaneous? The textbook questions 6O1 and 6O3 said to chose the reduction reaction with the most positive standard reduction potential for the cathode, but since this is an electrolytic cell, shouldn't that be the anode? Can someone please help me understand. Thanks!
In terms of electrolytic cells, it is important to keep in mind that it is not spontaneous, thus the voltage of the reduction reactions aren't super important because regardless of voltage, the cell will need additional energy to move the process.
The process of choosing which side the reaction will occupy in the cell diagram is the same regardless of the type of cell whether it is Galvanic or Electrolytic. However, conceptually, it is important to note that an input of energy will be needed for electrolytic cells regardless because they are designed to carry out non-spontaneous reactions (i.e. push electrons in the other direction).
The cell diagrams and the location of the cathode, anode, are the same in both an electrolytic cell and a galvanic cell. For both, oxidation still happens at the anode and reduction still happens at the cathode. In a galvanic cell, the anode has a negative charge and the cathode has a positive charge, causing the electrons to flow from the anode to the cathode. In an electrolytic cell, however, the anode has a positive charge and the cathode has a negative charge, causing electrons to flow from the cathode to the anode. A galvanic cell has a positive cell potential, and an electrolytic cell has a negative cell potential.
I understand what is being said, but if we are looking at the electrolytic cell problems (6O1, 6O3) they chose the half reaction with the highest reduction potential to be the cathode. Since it is electrolytic, shouldn't it be the lowest reduction potential?
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