Experiment 6: (Optional)

Which one Reacts?

Activity Series

Objective: An activity series of six substances can be developed from performing and observing a series of single replacement reactions.

Review of Scientific Principles:

When two different metals are in contact with each other or simply wetted with a solution containing sufficient ions to carry an appreciable electric current, an electrochemical cell is formed. The more active of the two metals will be consumed by the reaction.

Applications:

Understanding the chemistry of metals leads to the development of methods to reduce and prevent corrosion. Two metals may be used together; the more active one corrodes, sacrificing itself to save the other.

Time: 30 minutes

Materials and Supplies:

6 pieces of zinc, 1 cm by 1/2 cm

6 pieces of copper, 1 cm by 1/2 cm

6 pieces of magnesium, 1 cm by 1/2 cm

6 pieces of lead, 1 cm by 1/2 cm

optional - 6 pieces of iron

0.1 M AgNO₃ about 1 ml - 1.7g/100 ml

0.1 M CuSO₄ about 1 ml - 2.5 g/100 ml

0.1 M MgSO₄ about 1 ml - 1.2 g/100 ml

0.1 M ZnSO₄ about 1 ml - 2.9 g/100 ml

0.1 M Pb(NO₃)₂ about 1 ml - 3.3 g/100 ml

3 M HCl

24 hole cell well plate or 13 x 100 mm test tubes, rack, and test tube brush beral pipettes filled with the six solutions above forceps

General Safety Guidelines:

• Performing this experiment as a micro chemical lab requires less chemical and is generally safer.

• Proper eye protection should be worn.

Procedure:

1. Obtain a cell well plate and six pieces of each of the following metals: lead, copper, magnesium, and zinc.

2. Obtain six Beral pipettes each filled with a different solution. The needed solutions are 0.1 M silver nitrate, 0.1 M zinc sulfate, 0.1 M magnesium sulfate, 0.1 M lead (II) nitrate, 0.1 M copper (II) sulfate, and 3 M hydrochloric or sulfuric acid.

3. Note that the cell well plate has a number and letter grid. Place 20-25 drops of silver nitrate solution in cell well A1. Repeat this for B1, C1, and D1. It may be necessary to refill the pipette. Place 20-25 drops of zinc sulfate solution in each hole A2, B2, C2, and D2. Repeat this process remaining solutions until all of the cells are filled appropriately.

4. Using forceps, drop a sample of lead into cell well A1. Add another sample of lead to A2. Repeat this process until each of the cells in the A row contains a sample of lead. Record your observations.

5. Add a piece of copper to each of the cells in the B row, zinc to the C row cells, and magnesium to the D row. Record your observation after adding the metal samples to each row.

6. Using forceps remove and rinse each remaining piece of metal. Follow your teacher's directions as to disposal. Do not put the metal pieces down the drain. Add water to the plate and dump the contents in the receptacle provided.

Video Clip

Questions:

1. Draw a chart similar to the cell well plate and record your observations in that chart.

2. Write single replacement equations for those reactions that occurred.

3. Draw and fill in a chart showing which substance in each of the above reactions is more active and which is less active. The six substances for comparison are magnesium, silver, hydrogen, copper, lead, and zinc.

4. Which of the six substances always ended up less active? Which always ended up more active?

5. Use the chart you created in question 3 to rank the six substances from most active to least active.

Teacher Notes:

• If equipment is not available for micro-chemical analysis, test tubes can be substituted for the cell well. As mentioned previously, micro-chemical analysis is safer and results in less chemical to dispose of after the experiment.

Questions:

1. Student chart. The students should note reactions between any more active metal with a less active cation.

2. A sample reaction would be one between magnesium and copper (II) sulfate.

3-5. The order of activity, from most to least active, is: Mg Zn Fe Pb H Cu Ag