Question

By using the data in Appendix \(\mathrm{E}\), determine whether each of the following substances is likely to serve as an oxidant or a reductant: (a) \(\mathrm{Cl}_{2}(g),\) (b) \(\mathrm{MnO}_{4}^{-}(a q,\) acidic solution) (c) \(\mathrm{Ba}(s),\) (d) \(\mathrm{Zn}(s)\)

Short answer

Using Appendix E, we find that \(\mathrm{Cl}_{2}(g)\) and \(\mathrm{MnO}_{4}^{-}(a q,\) acidic solution) are oxidants due to their positive standard reduction potential values at +1.36 V and +1.51 V, respectively. Conversely, \(\mathrm{Ba}(s)\) and \(\mathrm{Zn}(s)\) are reductants, as they have negative standard reduction potential values at -2.92 V and -0.76 V, respectively.

Step-by-step solution

Locate Standard Reduction Potentials

Refer to Appendix E to find the standard reduction potential values for each given substance.

Determine Oxidant or Reductant for \(\mathrm{Cl}_{2}(g)\)

The standard reduction potential for \(\mathrm{Cl}_{2}(g)\) is: \(\mathrm{Cl}_2(g) + 2e^- \rightarrow 2 \mathrm{Cl}^-(aq)\) E° = +1.36 V Since the value is positive, \(\mathrm{Cl}_{2}(g)\) will act as an oxidant.

Determine Oxidant or Reductant for \(\mathrm{MnO}_{4}^{-}(a q,\) acidic solution)

The standard reduction potential for \(\mathrm{MnO}_{4}^{-}(a q,\) acidic solution) is: \(\mathrm{MnO}_4^-(aq) + 8\mathrm{H}^+(aq) + 5e^- \rightarrow \mathrm{Mn}^{2+}(aq) + 4\mathrm{H}_2\mathrm{O}(l)\) E° = +1.51 V Since the value is positive, \(\mathrm{MnO}_{4}^{-}(a q,\) acidic solution) will act as an oxidant.

Determine Oxidant or Reductant for \(\mathrm{Ba}(s)\)

The standard reduction potential for \(\mathrm{Ba}(s)\) is: \(\mathrm{Ba}^{2+}(aq) + 2e^- \rightarrow \mathrm{Ba}(s)\) E° = -2.92 V Since the value is negative, \(\mathrm{Ba}(s)\) will act as a reductant.

Determine Oxidant or Reductant for \(\mathrm{Zn}(s)\)

The standard reduction potential for \(\mathrm{Zn}(s)\) is: \(\mathrm{Zn}^{2+}(aq) + 2e^- \rightarrow \mathrm{Zn}(s)\) E° = -0.76 V Since the value is negative, \(\mathrm{Zn}(s)\) will act as a reductant. In conclusion, \(\mathrm{Cl}_{2}(g)\) and \(\mathrm{MnO}_{4}^{-}(a q,\) acidic solution) are oxidants, while \(\mathrm{Ba}(s)\) and \(\mathrm{Zn}(s)\) are reductants.

Key concepts

Oxidants

Oxidants, also known as oxidizing agents, play a crucial role in chemical reactions. They are substances that gain electrons during a chemical process. This means that they "oxidize" another substance by accepting electrons from it.
In essence, oxidants are electron acceptors. This process decreases the number of electrons in another substance, facilitating various chemical reactions in electrochemistry.Some key points to remember about oxidants include:

• Oxidants have a positive standard reduction potential (E°), suggesting they readily accept electrons.
• They are often found on the right side of a redox reaction.
• Common examples include substances like \( \mathrm{Cl}_2(g) \) and \( \mathrm{MnO}_4^-(aq) \) in acidic solutions, as they have high positive E° values.

Understanding the role of oxidants helps in predicting and balancing redox reactions, essential in both laboratory and industrial processes.

Reductants

Reductants, or reducing agents, serve an important function in redox reactions. Unlike oxidants, reductants lose electrons in reactions. Consequently, they "reduce" another substance by transferring electrons to it, allowing it to accept those electrons.
This characterizes reductants as electron donors in various reactions. Essentially, they increase the electron count in another molecule or atom.Consider these characteristics of reductants:

• Reductants have negative standard reduction potentials (E°), indicating they readily donate electrons.
• They are typically present on the left side of an electrochemical equation.
• The elements \( \mathrm{Ba}(s) \) and \( \mathrm{Zn}(s) \), for example, have negative E° values and act as effective reductants.

Grasping the behavior and purpose of reductants is fundamental in the study of electrochemistry and equipping oneself for complex redox equations.

Electrochemistry

Electrochemistry is a vital part of chemistry focusing on the interplay between electrical energy and chemical change. It involves the study of redox reactions where oxidation and reduction occur simultaneously, transferring electrons between substances.
This field centers around two main concepts: oxidants and reductants. By analyzing their interaction, we can better understand and utilize chemical processes that generate or are driven by electricity. Fundamental electrochemical concepts include:

• Standard Reduction Potentials (E°): These values help predict whether a substance will act as an oxidant or reductant by indicating its tendency to gain or lose electrons.
• Galvanic cells: Devices such as batteries that convert chemical energy into electrical energy using redox reactions.
• Electrolytic cells: Systems that drive non-spontaneous reactions through the application of electrical energy.

Electrochemistry not only enhances our understanding of academic concepts but also has practical implications, such as in the development of batteries, sensors, and corrosion prevention systems.