CHM 1045 Graves Chapter 4.6 Learning Objectives 4.10 Balance a simple redox equation using the half-reaction method Prep Assignments Reading Chapter 9.4 Iproblems 40-55] Balancing simple redox equations Things to remember Oxidation and reduction must happen together (a species must lose electrons and another species must gain them). . Number of electrons lost must be equal to number of electrons gained. The charges need to be balanced on both sides of the equation. Consider the following equation Cr (s) + Ni2+ (aq)â Cr3+ (aq) + Ni (s) Is this equation balanced? How can you tell? To balance we need to separate the reaction into two half reactions What does the term oxidation mean? What does the term reduction mean? Write down the oxidation half reaction Write down the reduction half reaction What do you notice about the side electrons are in the oxidation and reduction half reactions you wrote? What do you notice about the numbers of the electrons in the oxidation 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.
Hints
SubmitMy AnswersGive Up
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.
