From each of the following pairs of substances, use data in Appendix E to choose the one that is the stronger reducing agent: (a) Fe(s) or Mg(s) (b) Ca(s) or Al(s) (c) H2(g, acidic solution) or H2S(g)
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Identify the standard reduction potentials for both Fe(s) and Mg(s) from Appendix E. The standard reduction potential is a measure of the tendency of a chemical species to be reduced.
Compare the standard reduction potentials of Fe(s) and Mg(s). The substance with the more negative standard reduction potential is the stronger reducing agent.
Recall that a stronger reducing agent has a greater tendency to lose electrons, thus it is more easily oxidized.
Write the half-reactions for the reduction of Fe(s) and Mg(s) to understand how they gain electrons during the reduction process.
Conclude which substance is the stronger reducing agent based on the comparison of their standard reduction potentials and their tendency to lose electrons.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Reducing Agents
A reducing agent is a substance that donates electrons in a chemical reaction, thereby reducing another substance. The strength of a reducing agent is determined by its ability to lose electrons easily. Stronger reducing agents have a greater tendency to undergo oxidation, which is the loss of electrons.
Standard reduction potentials (E°) are measured values that indicate the tendency of a species to gain electrons and be reduced. These values are typically listed in tables, where a more positive E° value corresponds to a stronger oxidizing agent and a more negative value indicates a stronger reducing agent. Comparing the E° values of the substances in question helps determine which is the stronger reducing agent.
The electrochemical series is a list of standard reduction potentials for various half-reactions, arranged from the strongest oxidizing agents to the strongest reducing agents. By examining this series, one can predict the direction of redox reactions and identify which substances will act as reducing or oxidizing agents. This series is essential for comparing the reducing strengths of different metals.
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