Illustrated Guide to Home Chemistry Experiments

296 DIY Science: Illustrated Guide to Home Chemistry Experiments

POCEDURER
1.f you have not already done so, put on your splash I
goggles, gloves, and protective clothing.

2. Use steel wool or sandpaper to polish each of the
   electrodes to remove surface oxidation, oils, and other
   contaminants.


3. Use the knife to make two slits in the lemon, spaced as
   far apart as possible, and large enough to accept the
   electrodes. It’s important that the two electrodes do not
   touch once they are inserted into the lemon.


4. Insert the copper electrode in one of the slits and
   insert an electrode made of a different metal in the
   other slit.


5. Touch or clamp one of the leads from the DMM to each
   of the two electrodes and observe the reading on the
   DMM. If necessary, reverse the leads to obtain a positive
   voltage reading. Record the voltage reading to 0.01V in
   the appropriate cell of Table 16-4.


6. Leaving the copper electrode in position, remove the
   second electrode and replace it with another electrode
   of a different metal.


7. Use the DMM to record the voltage with this second
   pair of metals, and record that voltage to 0.01V in the
   appropriate cell of Table 16-4.


8. Repeat steps 6 and 7 until you have tested all
   combinations of the copper electrode with all of the
   other electrodes you have available.

FIGURE 16-2: Measuring the voltage produced by an

electrochemical cell with copper and zinc electrodes (note that the

actual voltage is lower than the theoretical 1.10V)

TABLE 16-4: Measure electrode potentials—observed data

ElectrodeMgAl znFe niSnPbCu

Mg ___.____V___.____V___.____V___.____V___.____V___.____V___.____V

Al ___.____V ___.____V___.____V___.____V___.____V___.____V___.____V

zn ___.____V___.____V ___.____V___.____V___.____V___.____V___.____V

Fe ___.____V___.____V___.____V ___.____V___.____V___.____V___.____V

ni ___.____V___.____V___.____V___.____V ___.____V___.____V___.____V

Sn ___.____V___.____V___.____V___.____V___.____V ___.____V___.____V

Pb ___.____V___.____V___.____V___.____V___.____V___.____V ___.____V

Cu ___.____V___.____V___.____V___.____V___.____V___.____V___.____V

9. Based on the voltage readings you obtained for copper
   with each of the other metals, choose one of those
   metals to replace the copper electrode. Test that metal in
   combination with all of the other metals. (But remember
   you’ve already tested it with copper.) Record the voltages
   you observe to 0.01V in the appropriate cells of Table 16-4.


10. Repeat step 9 until you have tested every metal paired
    with every other metal.