Electrochemical Cells Lab
Determination of an Electrochemical Series
In electrochemistry, a voltaic cell is a specially prepared system in which an oxidation-reduction reaction occurs spontaneously. This spontaneous reaction produces an easily measured electrical potential which has a positive value. Voltaic cells have a variety of uses and you commonly refer to them as a “battery”. Half-cells are normally produced by placing a piece of metal into a solution containing a cation of the metal (e.g., Cu metal in a solution of a soluble salt that releases Cu2+ or Cu+ into solution). In this micro-version of a voltaic cell, the half cell will be a small piece of metal placed into three drops of a solution on a piece of filter paper. The solution contains a cation of the solid metal. Figure 1 shows the arrangement of the halfcells on the piece of filter paper. The two half-reactions are normally separated by a porous barrier or salt bridge. Here, the salt bridge will be the filter paper soaked in an aqueous solution of potassium or sodium nitrate. Using a voltmeter, the positive terminal (or lead) makes contact with one metal and the negative terminal with another. If a positive voltage is recorded on the meter, the cell you have constructed is spontaneous and you have connected the cell correctly. To construct a spontaneous cell, attach the metal having a higher, more positive, reduction potential to the positive terminal which is the cathode. The metal attached to the negative terminal is the anode and has the lower, more negative, reduction potential.
By comparing the voltage values obtained for several pairs of half-cells, you can establish the reduction potential sequence for the five metals in this lab.
M1
M2
M5
M3
M4
Figure 1
OBJECTIVES
In this experiment, you will
• Prepare micro voltaic cells and measure their potential relative to a standard electrode. • Use
In electrochemistry, a voltaic cell is a specially prepared system in which an oxidation-reduction reaction occurs spontaneously. This spontaneous reaction produces an easily measured electrical potential which has a positive value. Voltaic cells have a variety of uses and you commonly refer to them as a “battery”. Half-cells are normally produced by placing a piece of metal into a solution containing a cation of the metal (e.g., Cu metal in a solution of a soluble salt that releases Cu2+ or Cu+ into solution). In this micro-version of a voltaic cell, the half cell will be a small piece of metal placed into three drops of a solution on a piece of filter paper. The solution contains a cation of the solid metal. Figure 1 shows the arrangement of the halfcells on the piece of filter paper. The two half-reactions are normally separated by a porous barrier or salt bridge. Here, the salt bridge will be the filter paper soaked in an aqueous solution of potassium or sodium nitrate. Using a voltmeter, the positive terminal (or lead) makes contact with one metal and the negative terminal with another. If a positive voltage is recorded on the meter, the cell you have constructed is spontaneous and you have connected the cell correctly. To construct a spontaneous cell, attach the metal having a higher, more positive, reduction potential to the positive terminal which is the cathode. The metal attached to the negative terminal is the anode and has the lower, more negative, reduction potential.
By comparing the voltage values obtained for several pairs of half-cells, you can establish the reduction potential sequence for the five metals in this lab.
M1
M2
M5
M3
M4
Figure 1
OBJECTIVES
In this experiment, you will
• Prepare micro voltaic cells and measure their potential relative to a standard electrode. • Use