Copper/Zinc Galvanic Cell (Daniel Cell)
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Description

The spontaneous chemical reaction between zinc metal and aqueous copper (II) sulfate is conducted so as to obtain the available chemical energy released in the form of electrical energy.


Set
Procedure
  1. Wear gloves. Use steel wool or sandpaper to polish 1.5- x 15-cm strips of copper and zinc sheet metal.
  2. Place 60 mL 1 M ZnSO4 solution in a 150-mL beaker. Place a polished zinc metal strip in the cup.
  3. Fill a porous cup three-fourths full with 1 M CuSO4 solution. Copper (II) sulfate solution will seep through the cup giving it a wet appearance. Place a polished copper metal strip in the cup. Place the porous cup inside the beaker. This arrangement of the two pieces of metal, the beaker, and the porous cup is called a cell.
  4. Connect alligator clip probes to a DC voltmeter. Connect the clips to the metal strips. Note and record the meter reading.
  5. Prepare a second cell using the procedure just described. Select a wire with alligator clips at each end. Connect the zinc strip in one cell with the copper strip of the other cell.
  6. Connect the alligator clips of the meter to the unconnected metal strips in the cells. Note and record the meter reading.
  7. Use the two-cell battery to drive low power devices. For example, a bank of light emitting diodes can be powered by the battery.
  8. Demonstrate alternatives for electrolytic connection of the half-cells. A salt bridge filled with an inert electrolyte (such as 1 M Na2SO4) may be used. A salt bridge consists of a U-tube filled with the electrolyte and stoppered with cotton or glasswool plugs.
  9. A salt bridge also may be constructed from paper. Form a U-shape from several layers of 1.5- x 15-cm filter paper strips. Insert one leg of the U-shape into the beaker with the zinc metal and zinc solution. Insert the other leg into the beaker with the copper metal and copper solution. Connect the meter to the metal strips. Moisten the paper U-shape with 1 M sodium sulfate solution.
  10. Note changes in the meter reading.

Handout Makeup

Name ___________________________ Class ________

Teacher__________________________

DoChem 116 Copper/Zinc Galvanic Cell (Daniel Cell)

Watch the movie.

  1. What is the role of the salt bridge?
  2. Why is the current low when the paper bridge is dry?

Teachers Guide

Purpose

To illustrate a galvanic cell.


Materials
Lab Hint


Time

Teacher preparation: 20 minutes

Presentation: 10-15 minutes


Hazards

The chemicals are toxic. Cuts from the metals strips and splinters from the steel wool are possible.


Precautions

Do not ingest the chemicals. Wear leather or canvas gloves when polishing the metal strips.


Disposal
Makeup Ans.
  1. The salt bridge makes an electrical connection which allows electrons to flow from one container to the next.
  2. Dry paper does not conduct electricity well. Ions in the solution conduct electricity through the paper bridge.

Key Words

This static was created at 12:31:56 PM on Monday, April 20, 2015