2.2 - Development of the Redox Table
Module 5
Lesson 2.2 Development of the Redox Table
Key Concepts
Redox tables are tables that display the relative strengths of oxidizing and reducing agents.
Redox tables are generated using empirical evidence. These tables can then be used to predict whether or not a redox reaction will be spontaneous.
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Empirical Evidence (Order of Reactivity)
Experimental data gathered over the years (from many reactions involving oxidizing agents and reducing agents) has served as the basis for the development of the "Table of Selected Standard Electrode Potentials", more simply known as a redox table. This table appears on page 7 of your data booklet and on page 828 of your textbook. A redox table lists oxidizing and reducing agents according to their relative strengths.
Watch
Read the lower half of page 569 to the end of the "Summary" section on page 571 of the textbook to learn more about how a redox table is developed using empirical (experimental) evidence.
Check Your Understanding
Complete Practice Questions 1-3 and 5-10 on page 571 of the textbook. Click on the link below to check your work.
Oxidation and reduction refer to the process of electron transfer; oxidizing and reducing agents refer to species that gain or lose electrons in an electrochemical process.
Page 571 Practice Question 2
Strong oxidizing agents have a strong affinity for electrons and promote the loss of electrons by other substances during a reaction.
Page 571 Practice Question 3
Strong reducing agents have a weak affinity for electrons and tend to lose electrons to other substances during a reaction.
Page 571 Practice Question 5
From "Table 1" on page 569 of the textbook or from "Table 2" on page 570 of the textbook, the metals that reacted spontaneously with copper(II) ion were lead and zinc.
Page 571 Practice Question 6
Silver metal did not react with copper(II) ion.
Page 571 Practice Question 7
In "Table 3" on page 570 of the textbook, a metal that reacted spontaneously with Cu2+(aq) appears below Cu2+(aq) in the table.
Page 571 Practice Question 8
Question 5 using Pb2+ instead of Cu2+: From "Table 1" or Table 2" the metal that reacted spontaneously with lead(II) ion was zinc.
Question 6 using Pb2+ instead of Cu2+: Silver metal and copper metal did not react with Pb2+.
Question 7 using Pb2+ instead of Cu2+: In "Table 3", the metal that reacted spontaneously with Pb2+ appears below Pb2+ in the table.
Page 571 Practice Question 9
Hypothesis: A spontaneous reaction will occur between a metal ion and a metal that is below it in Table 3.
Predictions based on Table 3 include that spontaneous reactions will occur between the following pairs:
- Ag+ and Cu
- Ag+ and Pb
- Ag+ and Zn
- Cu2+ and Pb
- Cu2+ and Zn
- Pb2+ and Zn
The predictions are correct according to the evidence collected in the experiment; therefore, the hypothesis is supported.
Page 571 Practice Question 10
Cl2(aq) + 2e- = 2Cl-(aq)
Br2(aq) + 2e- = 2Br-(aq)
I2(aq) + 2e- = 2I-(aq)
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Spontaneity Rule
The Redox Table (page 7 of your data booklet or page 828 of your textbook) demonstrates certain patterns and allows some empirical generalizations. Without having to conduct an experiment, we can use this redox table to predict whether a given reaction will be spontaneous or non-spontaneous. We can do this by applying the "Spontaneity Rule". The redox spontaneity rule is empirical in that it is based on observations of redox reactions.
The redox spontaneity rule is very important. If the oxidizing agent (OA) is located above the reducing agent(RA) on the Redox Table, the reaction will be spontaneous. If the oxidizing agent is located below the reducing agent on the Redox Table, the reaction will be non-spontaneous. Remember that the oxidizing agents are listed on the left-hand side of the Redox Table and the reducing agents are listed on the right-hand side.
Example 1
Is the combination of solid lead and Fe2+(aq) spontaneous or non-spontaneous?
Using the redox table, locate Pb(s) and Fe2+(aq). Because the OA is below the reducing agent, this is a non-spontaneous reaction.
Example 2
Is the reaction between solid lead and Fe3+(aq) spontaneous or non-spontaneous?
Using the redox table, locate Pb(s) and Fe3+(aq). Because the OA is above the reducing agent, this is a spontaneous reaction.
You have learned how chemists use degree of reactivity to construct a redox table (refer to pages 569 to 570 in your textbook). The spontaneity rule can be used for the same purpose.
Watch
Read page 572-573 of the textbook.
Check Your Understanding
Complete Practice Questions 11 to 14 on page 573 of the textbook and Practice Question 20 and 22 on page 574 of the textbook.
\( \mathrm { Co^{2+}(aq) + 2e^- \leftrightarrow Co(s) } \)
\( \mathrm { Zn^{2+}(aq) + 2e^- \leftrightarrow Zn(s) } \)
\( \mathrm { Mg^{2+}(aq) + 2e^- \leftrightarrow Mg(s) } \)
Page 573 Practice Question 12
\( \mathrm { Cu^{2+}(aq) + 2e^- \leftrightarrow Cu(s) } \)
\( \mathrm { 2H^+(aq) + 2e^- \leftrightarrow H_2(g) } \)
\( \mathrm { Cd^{2+}(aq) + 2e^- \leftrightarrow Cd(s) } \)
\( \mathrm { Be^{2+}(aq) + 2e^- \leftrightarrow Be(s) } \)
\( \mathrm { Ca^{2+}(aq) + 2e^- \leftrightarrow Ca(s) } \)
Page 573 Practice Question 13
The spontaneity rule is based on empirical evidence (experimental results).
Page 573 Practice Question 14
\( \mathrm { Cl_2(g) + 2e^- \leftrightarrow 2Cl^-(aq) } \)
\( \mathrm { Br_2(g) + 2e^- \leftrightarrow 2Br^-(aq) } \)
\( \mathrm { Ag^+(aq) + e^- \leftrightarrow Ag(s) } \)
\( \mathrm { I_2(s) + 2e^- \leftrightarrow 2I^-(aq) } \)
\( \mathrm { Cu^{2+}(aq) + 2e^- \leftrightarrow Cu(s) } \)
Page 574 Practice Question 20
- spontaneous
- non-spontaneous
- non-spontaneous
- spontaneous
- spontaneous
- spontaneous
Page 574 Practice Question 22
- React different combinations of oxidizing and reducing agents. The oxidizing agent that reacts spontaneously with the greatest number of reducing agents is the strongest. The oxidizing agent that reacts with the next greatest number of reducing agents is the next strongest and so on.
- Use the spontaneity rule to order the oxidizing agents and reducing agents.