Che 132 lecture 31: electrochemistry continued: electrochemical cells (voltaic cells. Anions have to migrate into the anode compartment to maintain the charge neutrality: on the cathode compartment cu2+ are consumed by the reduction reactions. In the left (anode) compartment the oxidation takes place: h2 (g) h+ (aq) It is convenient to tabulate cell voltages when reactants and products in the reaction are in standard conditions: pure solids, pure liquids, pure gases, pressure 1 bar, solutes at 1 mol l 1 concentrations. In such conditions voltages are referred to as standard voltages. By definition cell voltages for product favored reactions are positive. 0 > 0 (for a product-favored reaction: ecell, we can think of the standard cell voltage as the result of the standard voltages of the half cells. 0: ecell, e0 (cathode) and e0 (anode) are the standard voltages of the half-reactions. 0 - eanode written as reductions: only electrostatic potential differences can be measured; e0 (cathode) and.
Here, Zn undergoes oxidation by losing 2eâ, and the Cu2+ ions accept 2eâ to form metallic Cu, which is deposited at the copper electrode. At the zinc electrode, oxidation occurs, and hence it is known as the anode. Reduction occurs at the copper electrode, and hence it is called the cathode.
The electrochemical cell notation for this cell is Zn(s)|Zn2+(aq)||Cu2+(aq)|Cu(s).
Construction of a voltaic cell
Consider a chromium-silver voltaic cell that is constructed such that one half-cell consists of the chromium, Cr, electrode immersed in a Cr(NO3)3 solution, and the other half-cell consists of the silver, Ag, electrode immersed in a AgNO3 solution. The two electrodes are connected by a copper wire. The Cr electrode acts as the anode, and the Ag electrode acts as the cathode. To maintain electric neutrality, you add a KNO3 salt bridge separating the two half-cells. Use this information to solve Parts B, C, and D.
Part B
The half-cell is a chamber in the voltaic cell where one half-cell is the site of the oxidation reaction and the other half-cell is the site of the reduction reaction.
Type the half-cell reaction that takes place at the anode for the chromium-silver voltaic cell. Indicate the physical states using the abbreviation (s), (l), or (g) for solid, liquid, or gas, respectively. Use (aq) for an aqueous solution. Do not forget to add electrons in your reaction.
Express your answer as a chemical equation.
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Part C
The half-cell is a chamber in the voltaic cell where one half-cell is the site of an oxidation reaction and the other half-cell is the site of a reduction reaction.
Type the half-cell reaction that takes place at the cathode for the chromium-silver voltaic cell. Indicate physical states using the abbreviation (s), (l), or (g) for solid, liquid, or gas, respectively. Use (aq) for an aqueous solution. Do not forget to add electrons in your reaction.
