Illustrated Guide to Home Chemistry Experiments

dISoALp S : The hydrochloric acid waste can be

neutralized with sodium carbonate or sodium

bicarbonate and flushed down the drain with copious

water. The electrodes can be retained for later use.

POCEDURER
1.ou have not already done so, put on your splash If y
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. Transfer about 200 mL of 2 M hydrochloric acid to
   the beaker.


4. Clamp one of the patch cables to the copper electrode
   and the other patch cable to the magnesium electrode.


5. Clamp the remaining end of each patch cable to one of
   the wires that extends from the base of the LED.


6. Immerse both electrodes in the beaker of hydrochloric
   acid. If the LED does not light, reverse the leads. The light
   emitted by the LED represents work done by the electric
   current produced by an electrochemical reaction.


7. Leaving the copper electrode in position, remove the
   magnesium electrode, disconnect it from the patch cable,
   and rinse it thoroughly with water.


8. Connect the iron electrode to the patch cable, and
   immerse the iron electrode in the beaker of hydrochloric
   acid. The LED should not illuminate.


9. Disconnect both leads from the LED and reconnect them
   to the DMM. Verify that the voltage across the copper/
   iron electrode pair is approximately 0.78V.
   Remove the iron electrode from the acid bath and rinse it
   thoroughly with water.
   Immerse only 1 cm of the iron electrode in the acid bath,
   and use the DMM to record the voltage and current
   (amperage) on the first line of Table 16-5.
   Increase the distance the iron electrode is immersed in
   the acid bath centimeter by 1 centimeter, recording the
   voltage and current at each immersion level in Table 16-5.

10.

11.

12.

FIGURE 16-3:

Measuring the current produced by an electrochemical cell

TABLE 16-5:

Observe energy transformation—observed data

Level voltageCurrent

1 cm___.____V____.___ mA

2 cm___.____V____.___ mA

3 cm___.____V____.___ mA

4 cm___.____V____.___ mA

5 cm___.____V____.___ mA

6 cm___.____V____.___ mA

7 cm___.____V____.___ mA

8 cm___.____V____.___ mA

Chapter 16 Laboratory: Electrochemistry 299