Click to zoom Electrochemical Cells The tendency of oxidation-reduction reactions is to proceed to an equilibrium state. These reactions occurring in electrochemical cells provide another way for us to express the driving force in chemical reactions. When reagents that accept or donate electrons are arranged so that the electrons can enter or leave the reaction through a metallic conductor, an electrochemical cell is established. A half-cell contains a metal in contact with a solution of its salt.
Obtain and wear goggles. Use steel wool to clean a brass key and a strip of copper, which will be the electrodes of the electrochemical cell. Mix 3 g of NaCl with 15 mL of vinegar in a mL beaker.
Rinse the key and copper strip with distilled water and dry each metal piece. Use an analytical balance to determine the mass of the key and the mass of the copper strip. Record these two masses in your data table.
The electrolyte solution in this experiment is prepared in H2SO4 and should be handled with care. Attach a 7 cm length of bare copper wire to the brass key to act as a handle.
Connect the wire to the alligator clip for the anode, so that the key will be completely immersed in the electrolyte solution but the alligator clip will not be immersed. Connect the copper strip to the positive lead. You will not place the electrodes in the beaker until Step Use connecting wires, with alligator clips, to connect the DC power supply, Current Probe, and the electrodes.
See Figure 1 for the proper setup of the wiring.
If you have an older sensor that does not auto-ID, manually set up the sensor. Change the data-collection rate to 0. Place the key and the copper strip into the electrolyte solution in the beaker. Make sure that the key is completely immersed in the solution, and keep the two electrodes as far apart as possible.
Turn on the DC power source and check the sensor readings. The initial current should be in the 0. If the current is not in this range, check with your instructor before proceeding.
Note the slow deposition of copper on the surface of the key. The data collection will run for 30 minutes. When the data collection is complete, turn off the DC power source and carefully remove the copper strip and key from the electrolyte solution. Rinse the two metals with distilled water.
Dry the copper strip and key very carefully, so as not to remove copper. Determine the average current applied during the experiment. Choose Statistics from the Analyze menu.
Record the mean in your data table as the average current. Measure and record the mass of the dry copper strip and key. Discard the electrolyte solution and take care of the electrochemical cell as directed.
Calculate the number of coulombs of charge passed through the electrolytic cell.
Calculate the theoretical number of moles of copper that should have plated out onto the brass key. Calculate the actual number of moles of copper that plated out. Calculate the percent yield of copper.
Suggest the sources of error in your experiment. Write the oxidation and reduction half-reactions for this process.VWR International, a global laboratory supplier and distributor of chemicals, life science products, consumables, equipment, instruments, furniture, e-commerce and services.
Electrolytic Cells A second type of electrochemical cell is the electrolytic cell.
This is one in which an external electric current is used to drive a non-spontaneous chemical reaction (Figure 1).
electrochemical cell. The standard reduction potential is the voltage that a half-cell, under standard conditions (1 M, 1 atm, 25°C), develops when it is combined with . The importance of electrochemical cells or galvanic cells lies in their ability to provide us with a portable source of electrical energy.
We have already studied that indirect redox reaction is, primarily, the basis of all the electrochemical cells Quite often, we use the term battery to represent the arrangement of two or more galvanic cells connected in series.
Honour Chemistry Lab #10 Page 1 of 4. Lab # Electrochemical Cells Objectives: 1. To understand the nature of electrochemical cells. The objective of the first part of the lab is to determine the cell potential (Ecell) for various voltaic cells and compare the data with the calculated E cell values obtained by using the Nernst equation.