I’m having a difficult time figuring this out since oxidation always occurs at the anode, and this would be where electrons are produced.
Is it this: in voltaic cells, the reaction is spontaneous and does not require a current. So oxidation of the element etc. occurs on its own, and electrons are produced. Because electrons move spontaneous from negative to positive, the anode (where electrons are produced) must be negative or else the electrons would be moving from positive to negative which does not make sense, unless they were forced to do this (like in an electrolytic cell)
One Response
A voltaic cell represents a spontaneous reaction. You are correct in that oxidation always occurs at the anode, regardless of the type of cell. Since oxidation is the loss of electrons, an element (typically a metal) will be losing electrons and forming ions in solution at the anode.
As an example we have a cell made from two compartments in which there is copper metal in copper sulfate and zinc metal in zinc sulfate. The zinc spontaneously loses electrons to be oxidized to Zn2+ while Cu2+ are reduced to copper metal, which is the cathode. Zinc is the anode and copper the cathode.
An electrolytic cell is nonspontaneous chemical reaction. In order to make a reaction occur, a voltage must be supplied to force electrons to flow. Suppose that in an electrolytic cell, electrons are supplied by the power supply (negative pole) to the zinc metal, where the Zn2+ ions acquire two electrons and plate out as zinc metal, while the copper metal loses two electrons and forms Cu2+ ions. The zinc is reduced (its the cathode, now) and the copper is oxidized (it’s the anode, now).