Voltaic Cells

If you are absent, click here and follow the directions.

This will go in your lab book. Follow the directions to complete the lab.

Purpose (put into lab book)

• The purpose of this lab is to create several voltaic cells, determine the voltage we would expect to be produced using the orange sheet, and determine the actual voltage produced using a voltmeter.

Background (summarize into lab book)

• Use your notebook to define a voltaic cell and write down the key parts of a voltaic cell and any important information about them.

• Copy the % error formula into your background.

• We will be using Iron (III) today in lab. Iron (III) is not on your orange reference sheet. Add the half reaction and voltage on to your orange sheet. MAKE SURE YOU PUT IT IN THE PROPER LOCATION ON THE ORANGE SHEET!

  • • Fe⁺³ + 3e^-1 --> Fe V = - 0.04V

Procedure (summarize in lab book)

1. You are given in the back of the room three metals (Cu(II), Fe(III), and Zn), their corresponding solutions, a porous cup (similar to a salt bridge), and a voltmeter.

2. Build a voltaic cell using any pair of metals.

3. Fill the porous cup about half way with the solution of one of the metals and put in the bar of that metal.

4. Fill the beaker with about 75 mL (does not need to be exact) of the solution of the other metal and put in the bar of that metal. Then put the porous cup inside the beaker.

5. Connect one wire from the anode to the black negative knob on the voltmeter. (you need to determine which metal this is)

6. Connect the other wire from the cathode to the second knob from the left (3V) on the voltmeter. If your needle moves backward then switch the two wires. If you are not getting a reading at all, reposition the clips.

7. Read and record the experimental voltage. Notice the voltmeter has multiple scales. You will be reading the voltage using the bottom scale (0 - 3).

8. Repeat for the two other metal combinations.

Data

Starting on a brand new page, copy this exact set up three times on the next three pages as shown below. Use the entire page for each!

• • Diagram - in this area you will draw a diagram of the cell, labeling all the parts and showing the flow of electrons. Draw your picture as if you were using a salt bridge (even though we are using a porous cup) because it is easier to draw. Put NaCl in your salt bridge.

  • Calculated Voltage - this is the voltage you calculate using the orange sheet (honors: the solutions are 0.1 M, not 1 M - Show formula, substitution, and calculations)

  • Experimental Voltage - this is the voltage you read off of the voltmeter

  • Percent Error - show formula and calculations!