UNIT 05: Redox Reactions
BCLN CHEMISTRY 12 - Rev. July, 2015
Project: Corrosion of Iron
Potential Credits:
Name: ________________
/15
Goal:
The goal of this lab is to help you acquaint you with the process of corrosion and to investigate how it
can be slowed. You will be provided with data from an experiment in which Iron nails were placed
in test tubes containing various solutions and/or other metals and asked to analyze this data. Finally
you will be asked to answer some questions about the results and concepts.
Iron and Corrosion Research Questions:
Google and/or Wikipedia will be helpful in answering these questions.
1. Iron is the fourth most abundant element by mass in the earth's crust after oxygen silicon and
aluminum. Iron is the second most abundant metal after aluminum. However it is more widely used
than aluminum. Find a reason why this is the case.
2. Most iron is converted into steel before use. Which other element is most commonly alloyed with
iron to create steel?
3. What is the biggest drawback of using Iron over Aluminum? Hint: Check the title of this project!
4. What are the two common oxidation numbers of iron?
5. What does it mean to "galvanize" iron?
6. What is the common name for the substance formed when Iron corrodes? Hint you see it on old
cars.
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UNIT 05: Redox Reactions
BCLN CHEMISTRY 12 - Rev. July, 2015
Procedure:
NOTE: You do NOT need to actually do this experiment. The procedure is presented here for
your information and you will be given the results below.
1. Eleven regular iron nails are placed in test tubes. One galvanized iron nail is also placed in a test
tube and they are labeled 1 through 12.
2. Various solutions are added to each test tube as shown in the data table.
3. The first observation is made 5 days later. The second observation is made 5 days after the first
observation. An example of what this might look like is shown in the picture below:
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UNIT 05: Redox Reactions
BCLN CHEMISTRY 12 - Rev. July, 2015
Data Table:
First
Observation
Number
Contents
1
Filled with Water (Control)
Some Rust
More Rust
5
2
Half Water, Half Air
Some Rust
More Rust
7
3
Filled with 0.05 M NaCl
(Table Salt)
Some Rust
More Rust
8
4
Filled with 0.05 M HCl
Yellow Solution
Yellow Solution.
10
5
Filled with 0.05M NaOH
No Change
No Change
1
6
Air only
No Change
No Change
1
7
Boiled Water (Air has been No Change
removed from the water)
Tiny amount of
rust
3
8
Zinc wrapped around nail. No Change
Filled with water
Tiny amount of
rust
3
9
Magnesium wrapped around No Change
nail. Filled with water.
Tiny amount of
rust
2
10
Copper wrapped around Some Rust
nail. Filled with water
More Rust
8
11
Grease coated nail. Water
No Change
No Change
1
12
Galvanized nail. Water
No Change
No Change
1
Page 3 of 6
Second
Observation
Amount of
Corrosion (Larger
Number indicates
more corrosion)
UNIT 05: Redox Reactions
BCLN CHEMISTRY 12 - Rev. July, 2015
Analysis:
1. When you compare test tube 6 to test tube 1 it should be obvious that water is necessary for
corrosion. Compare test tube 7 to test tube 1, what else is required for corrosion?
2. Specifically, what component of your answer above is required for corrosion?
3. Look at the results from test tubes 1, 3, 4 and 5 and rank salt, base, acid and water in terms of how
much they increase corrosion.
4. The corrosion of iron is a multi step process. The first step is to oxidize Iron into Iron(II) ions.
Look this up on the Standard Reduction Potentials of Half Cells chart in your data booklet and record
the reaction and the Eo value below. As this is an oxidation reaction you must reverse the sign on the
Eo value.
5. A redox reaction always requires both oxidation and reduction. This means we need an oxidizing
agent. In this case that agent is the answer to question 2. There are two equations for the reduction
of this element from the Standard Reduction Potentials of Half Cells. One in neutral water (10-7 M),
one in 1 M acid. Write these reactions below with their Eo values.
6. Which of the above reactions will proceed more quickly, acid or neutral water? Explain. Does
this agree with the results from the experiment (test tubes 1 and 4)?
7. Iron(II) ions can be further oxidized to form Iron(III) ions. Write this oxidation reaction with its
Eo value below.
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UNIT 05: Redox Reactions
BCLN CHEMISTRY 12 - Rev. July, 2015
8. The reduction reaction in this experiment uses up H+ ions. This produces OH- ions in solution.
What you see as rust is a precipitate that forms between Iron(III) ions and hydroxide ions. Write this
reaction below.
9. Compare the results for test tubes 8,9 and 10. Which metal(s) slowed corrosion and which
metal(s) hastened corrosion?
10. Explain the above results using the Standard Reduction Potentials of Half Cells table in your data
booklet.
11. Explain the results of test tube 11.
12. Explain the results of test tube 12.
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UNIT 05: Redox Reactions
BCLN CHEMISTRY 12 - Rev. July, 2015
Further Investigation:
1. Blocks of magnesium are connected at intervals to hulls of ships to prevent the corrosion of iron.
They are called "sacrificial anodes" since they sacrifice themselves to prevent the iron from corroding
but this means they need to be replaced periodically. Why does it make economic sense to replace
the blocks of magnesium?
2. As opposed to magnesium, galvanized objects do not need their metal replaced. Do some research
and determine why this is so.
3. Explain why the salts put on winter roads to melt ice can hasten the corrosion of a car.
4. Some tools made of iron are not able to be plated. Based on your results can you suggest a
method of protecting these tools when they are stored?
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