Lab 13 - Redox Reactions

What effect will this have on the measurement if the

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Unformatted text preview: ouple is the cathode; with the Ag+/Ag couple it was the anode. What effect will this have on the measurement? If the Cu2+/Cu couple is maintained at the same terminal of the voltmeter for all the measurements, those in which it is the cathode will show negative potentials. This simply indicates that electrons are traveling through the voltmeter in the opposite direction from what was measured in the cell with the Ag+/Ag couple. Voltmeters are sensitive to the direction of electron flow (electrical current), and indicate the direction by means of the sign on the potential difference. Therefore, with this 2+/Cu couple is the anode, and a negative voltage experimental set- up, a positive voltage means that the Cu means that the Cu2+/Cu couple is the cathode. Thus, you should obtain a series of potential differences that can be arranged from most negative to most positive. This order will tell you the energy relationships between filled orbitals in the metals and vacant orbitals in the ions. The couple that produces the most negative potential www.webassig encheml1/lab_13/manual.html 4/10 4/15/13 Lab 13 - Redox Reactions difference with copper will have the metal with the highest energy electrons. It will be the strongest reducing agent. The couple that produces the most positive potential difference with copper will have the lowest energy unfilled orbitals. It will be the strongest oxidizing agent. For Part B, you will use a simple version of an electrochemical cell. It will consist of two plastic containers that act as the individual cells and a salt bridge. The metal electrodes are wires that will be placed into the solutions containing metal ions. When the leads of the voltmeter are connected to the two metal electrodes, the potential difference between the two cells will be measured just as in Figure 2 above. Equipment Part A: Relative Reactivities 1 ceramic spot plate 3 30 mL beakers 1 deionized water squirt bottle Part B: Half-Cell Potentials 4 electrochemical cell set- ups on the side shelf of the lab Reagents Part A: Relative Reactivities ~6 drops 0.1 M Cu(NO3)2 ~6 drops 0.1 M Mg(NO3)2 ~6 drops 0.1 M KMnO4 (acidic) ~9 drops 3% H2O2 solution ~9 drops 0.1 M KI ~9 drops phenolphthalein solution ~2 pieces Cu metal ~2 pieces Zn metal ~2 pieces Mg metal ~20 mL 3 M HCl ~30 m...
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This document was uploaded on 01/22/2014.

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