Module 3
1. Module 3
1.20. Page 2
Module 3—Electrochemical Reactions
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Iron Corrosion
The corrosion of iron is a complex electrochemical process. Steel is primarily composed of iron. Its corrosion occurs more frequently in moist conditions in which the iron is also exposed to oxygen.
The process of corrosion involves more than a simple oxidation of iron to Fe2+. Iron(II) ions further undergo a reaction to form rust, which has the chemical formula Fe2O3 • nH2O(s).
TR 1. Identify the strongest oxidizing and reducing agent in the initial reaction of iron described in the first paragraph of the passage above.
TR 2. Identify whether the change in iron that forms rust, described in the second paragraph, is an oxidation or a reduction. Support your answer.
Submit your answers to your teacher for feedback. Save a copy of your answers in your course folder, as you may wish to refer to them later in this lesson.
Read
How did you determine that iron was undergoing a change in TR 1 and TR 2? Did you focus on the charge on the iron atom? For metals, determining whether a reduction or an oxidation has occurred often requires you to look at how the charge of the metals changes. What about non-metals and atoms within polyatomic ions? How is their oxidation or reduction tracked?
Read pages 583–585 in the textbook. You may wish to save a copy of the information in “Table 1” on page 583 in your course folder.
Earlier in this module you compared the charge of copper atoms and copper ions. When doing so, you were using the oxidation numbers for these forms of the copper atom. Using oxidation numbers is a quick and useful way to obtain information about electrochemical change. Since oxidation numbers are a powerful tool in analysis of electrochemical systems and you will not always be able to access this information in your Chemistry Data Booklet, you will have to memorize the information in this table.
Self-Check
SC 1. Complete “Practice” questions 1–5 on page 585 of the textbook.
Read
At the beginning of this lesson you were asked to consider how the electrochemical change in atoms could be tracked. Can oxidation numbers be used to identify the oxidized and reduced species (reducing agent and oxidizing agent respectively) in a balanced chemical equation? Read the text and work through the “Sample problems” and “Communication examples” on pages 585–588 of the textbook to find out.
Self-Check
SC 2. Complete “Practice” questions 6–9 on page 588–589 of the textbook.