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Reactivity & Electrochemistry (3 Favorites)

LAB in Electricity, Reduction, Activity Series, Redox Reaction, Reduction Potentials, Oxidation, Electron Transfer, Electrons. Last updated October 14, 2019.


Summary

In this lab, students will relate cell potential to the activity series.

Grade Level

High school

AP Chemistry Curriculum Framework

This lab activity supports the following units, topics, and learning objectives:

  • Unit 4: Chemical Reactions
    • Topic 4.7: Types of Reactions
      • TRA-2.A: Identify a reaction as acid-base, oxidation-reduction, or precipitation.
  • Unit 9: Applications of Thermodynamics
    • Topic 9.7: Galvanic (Voltaic) and Electrolytic Cells
      • ENE-6.A: Explain the relationship between the physical components of an electrochemical cell and the overall operational principles of the cell.

Objectives

By the end of this lesson, students should be able to

  • define oxidation and reduction in terms of loss or gains of electrons.
  • interpret the activity series in terms of elements that are more or less easily oxidized.
  • describe redox reactions in terms of the movement of electrons (oxidation and reduction).
  • understand that electrons can be transferred from one metal to another in a redox reaction.
  • relate cell potential to the activity series.

Chemistry Topics

This lesson supports students’ understanding of

  • Electrochemistry
  • Activity series

Time

Teacher Preparation: 1 hour

Lesson: 1 class period

Materials

For each group:

  • Four small pieces of each of the following:
    • Copper foil
    • Iron nail
    • Magnesium ribbon
    • Zinc strip
  • The following solutions:
    • 1 M Cu(NO3)2 (aq)
    • 1 M Fe(NO3)2 (aq)
    • 1 M Mg(NO3)2 (aq)
    • 1 M Zn(NO3)2 (aq)
    • 1 M KNO3 (aq)
  • Steel wool
  • Wire and alligator clips
  • Voltmeter or multimeter

Safety

  • Always wear safety goggles when working with chemicals in a lab setting.
  • It’s recommended students wear gloves when using steel wool, to avoid any cuts from the roughness of the steel wool.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

  • If students are having difficulty testing voltages in part B, make sure that the KNO3 solution has not dried up.

For the Student

Lesson

Background

Some substances give up or accept electrons easier than others and can be organized by their relative ability to undergo oxidation or reduction. An element that loses electrons more easily (more easily oxidized) is referred to as more active. If two elements are in physical contact, a redox reaction may occur. In this lab, two elements will be “connected” through three methods: by placing a piece of a metal in an aqueous salt of another metal; through a thin wire; and using an inert electrolyte (KNO3). Investigating what happens when any two elements are “connected” will predict whether or not a redox reaction will occur, whether there will be an electric current, and which direction the electrons are flowing.

Purpose

Relate cell potential to the activity series.

Materials

4 small pieces of each metal: Solutions: Other:
Copper foil, Cu(s) 1M Cu(NO3)2 Steel wool
Iron nail, Fe(s) 1M Fe(NO3)3 Wire/alligator clips
Magnesium ribbon, Mg(s) 1M Mg(NO3)2 Voltmeter/multimeter
Zinc strip, Zn(s) 1M Zn(NO3)2 12-well reaction plate
1M KNO3 Filter paper/pipettes

Safety

  • Always wear safety goggles when working with chemicals in a lab setting.

Procedure

Part A. Reactivity of Metals

Use your knowledge of the periodic table and real world experience to predict which metal will be the most reactive and which will be the least reactive.

Prediction:
Prepare the metal pieces by using the steel wool to remove any discoloration from the metal surface.

  • Using two well plates, add ten drops of each salt solution to each well of the appropriate columns.
  • Add a small piece of copper to each well in the first row. Record your observations in Data Table 1.
  • Repeat with iron, magnesium, and zinc in rows two through four.

Data Table 1

Figure 1

Cu(NO3)2 Fe(NO3)2 Mg(NO3)2 Zn(NO3)2
Cu
Fe
Mg
Zn

Part B: Simple Electrochemical Cells

Review the data from Part A; predict which metal is most easily oxidized and which metal is most easily reduced.
_______________________________________________________________________________
_______________________________________________________________________________

(Hint: Solid metals must lose electrons to become ions and dissolve in solution.)

This pair should produce the largest electric potential when connected by the voltmeter (absolute value of voltmeter reading). Predict which pair of metals will produce the largest electric potential.

Prediction:
_______________________________________________________________________________
_______________________________________________________________________________

  1. Fold a circular piece of filter paper so that there are four sections. (Refer to Figure 1)
  2. Place a small piece of each metal on the filter paper as shown in Figure 1.
  3. Place two–three drops of the corresponding salt onto each metal, as shown in Figure 1.
  4. Add enough KNO3 to the middle of the filter paper so that the moisture reaches all of the metals.
  5. Use the voltmeter probes to connect copper to iron. Record the reading, including the + or - sign, in Data Table 2.
  6. Repeat for copper and magnesium, and copper and zinc.
  7. Repeat steps five and six until data is collected for every possible pair of metals.

Data Table 2

Cu-Fe


Cu-Mg Fe-Mg

Cu-Ag Fe-Ag Mg-Ag
Cu-Zn Fe-Zn Mg-Zn Ag-Zn

Analysis

  1. In Part A, which solid metal was the most reactive with the aqueous ionic compounds?
  2. Did this metal gain or lose electrons in these reactions? Explain.
  3. Which aqueous ionic solution formed a precipitate most often in reactions?
  4. This precipitate is a solid metal formed from the ions in solution. Did this metal gain or lose electrons to form a solid? Explain.
  5. Rank the four metals from most active to least active. Compare your list to the activity series shown on the board.
  6. In Part B, what was the purpose of the KNO3?
  7. In Part B, which pair of metals produced the highest voltage reading?
  8. Draw a diagram showing the direction of the flow of electrons for this pair of metals. The data from Part A is useful here. Label the metal that is oxidized; label the metal that is reduced.
  9. Write a statement that summarizes the relationship between Part A and Part B.