Name __________________________________ Date ____________ Class ____________
PRELAB ASSIGNMENT
Oxidation–Reduction Reactions
1. How are oxidation and reduction defined?
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
2. When a metal reacts with an acid, what is oxidized and what is reduced in the reaction?
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
3. What characterizes a strong reducing agent?
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
4. What will you do with the metal strips when you have finished testing them?
_______________________________________________________________________________
_______________________________________________________________________________
Name __________________________________ Date ____________ Class ____________
COMPARATIVE LAB
Oxidation–Reduction Reactions
PURPOSE
To investigate and compare the relative reduction potentials of copper,
lead, and zinc in oxidation–reduction reactions.
BACKGROUND
The rusting of iron and the combustion of gasoline are common examples
of oxidation–reduction reactions. Oxidation reactions are also thought to
be partly responsible for the aging of the human body. Every oxidation
reaction involves a transfer of electrons from the substance oxidized to the
substance reduced. A substance undergoing oxidation gives up, or loses,
electrons; a substance undergoing reduction gains electrons. The ease with
which a substance oxidizes depends on the substance. For example, iron
oxidizes more easily than either silver or gold.
In this experiment, you will study some oxidation–reduction reactions
that occur between metals and metal ions. On the basis of your
experiments, you will organize these substances into a series according to
their relative ease of oxidation.
MATERIALS (PER PAIR)
safety goggles
3 shots of zinc, Zn, each
glass-marking pencil
96 well reaction tray
plastic wash bottle
3 shots of copper, Cu, each
3 strips of lead, Pb, each
0.1M copper(II) nitrate,Cu(NO3)2 T
0.1M lead(II) nitrate, Pb(NO3)2 T
0.1M zinc nitrate, Zn(NO3)2 I
1.0M hydrochloric acid, HCl
SAFETY FIRST!
In this lab, observe all precautions, especially the ones listed below. If you
see a safety icon beside a step in the Procedure, refer to the list below for
its meaning.
Caution: Wear your safety goggles. (All steps.)
Caution: Use a piece of paper or gloves to hold the steel wool to
avoid getting metal slivers in your hand. (Steps 1, 2.)
Caution: Hydrochloric acid is corrosive and can cause severe
burns.
Caution: Copper and lead compounds are toxic. (Steps 2, 3.)
Note: Return or dispose of all materials according to the
instructions of your teacher. (Step 6.)
Name __________________________________ Date ____________ Class ____________
PROCEDURE
As you perform the experiment, record your observations in Data Table 1.
1.
Polish the small metal strips of copper, lead, and zinc with
steel wool.
2.
Label three test tubes “0.1M Cu(NO3)2.” Add 3 mL of 0.1M
copper(II) nitrate to each test tube. In one tube, place a strip
of copper. In another, place a strip of lead. In the third, place
a strip of zinc. Put the tubes in a test-tube rack.
3.
Repeat Step 2 with three new test tubes, labeling the tubes
“0.1M Pb(NO3)2” and using 0.1M lead(II) nitrate in place of
copper(II) nitrate.
4.
Repeat Step 2 with three new test tubes, labeling the tubes
“0.1M Zn(NO3)2” and using 0.1M zinc nitrate in place of
copper(II) nitrate.
5.
Repeat Step 2 with three new test tubes, labeling the tubes
“1M HCl” and using 1M hydrochloric acid in place of zinc
nitrate.
6.
7.
Allow the test tubes to stand undisturbed for 5–10 minutes.
Record your observations in Data Table 1, briefly describing
evidence of any reaction.
Return the metal strips for reuse and dispose of the solutions
as instructed by your teacher.
OBSERVATIONS
DATA TABLE 1: REACTIONS OF METALS AND METAL IONS
Cu2+
Cu(s)
Pb(s)
Pb2+
Zn2+
H1+
X
X
Zn(s)
X
ANALYSES AND CONCLUSIONS
1. Write balanced equations for any reactions that you observed between solid metals and metal ions.
2. Which metal was oxidized by both of the other two metals?
3. Which metal was oxidized by only one of the other two metals?
4. Which metal was oxidized by neither of the other metals?
5. Which metal(s) out of the ones we tested were the most reactive? Which was/were the least
reactive?
6. Suggest another chemical you could use to clarify your results and determine the MOST reactive
metal from the group. Explain why you would use this chemical.
Name __________________________________ Date ____________ Class ____________
GOING FURTHER
Develop a Hypothesis
Many metals, including the ones examined in this lab, are oxidized by aqueous solutions of acids to
produce hydrogen gas and metal ions. Based on the results of this lab, propose a hypothesis about the
relative ease with which lead, copper, and zinc would be oxidized by an acid. Extend your hypothesis
to include other metals such as iron, tin, and aluminum and discuss any periodic trends in oxidation by
acids that would exist for the various metals.
Design an Experiment
Propose an experiment to test your hypothesis. If resources are available and you have your teacher’s
permission, perform the experiment.
Name __________________________________ Date ____________ Class ____________
Name __________________________________ Date ____________ Class ____________