Problem 83 - General Chemistry: Principles and Modern Applications

Question

The best oxidizing agent of the following group of ions is (a) \(\mathrm{Ag}^{+}(\mathrm{aq}) ;\) (b) \(\mathrm{Cl}^{-}(\mathrm{aq}) ;\) (c) \(\mathrm{H}^{+}(\mathrm{aq})\) (d) \(\mathrm{Na}^{+}(\mathrm{aq}) ;\) (e) \(\mathrm{OH}^{-}(\mathrm{aq})\)

Step-by-Step Solution

Answer

The best oxidizing agent among the given ions is Ag+.

Step 1: Understanding Oxidizing agents

An oxidizing agent causes the oxidation of other substances by taking their electrons and is itself reduced in the process. Thus, it can be evaluated with their reduction potential. The species with the highest reduction potential is typically the strongest oxidizing agent.

Step 2: Identifying the strongest oxidizing agent

Looking to the standard reduction potentials for ions, the ions with more positive reduction potentials are the stronger reducing agents. The given ions are: Ag+, Cl-, H+, Na+ and OH-. Referring to a table of standard reduction potentials, these species have the following potentials: \n\nAg+ + e- -> Ag (Eº = +0.80 V)\n2H+ + 2e- -> H2 (Eº = 0.00 V)\n2Cl- -> Cl2 + 2e- (Eº = -1.36 V)\nNa+ + e- -> Na (Eº = -2.71 V)\n2OH- -> O2 + H2O + 4e- (Eº = -0.40 V)

Step 3: Result

From the reduction potentials, the Ag+ ion has the most positive (hence the highest) reduction potential. Therefore, among the options, it is the best oxidizing agent.

Key Concepts

Standard Reduction Potential

In the world of chemistry, understanding the standard reduction potential is crucial for determining the behavior of ions during chemical reactions. The standard reduction potential indicates the tendency of a species to gain electrons, thus becoming reduced.
This potential is measured in volts and often expressed using a half-reaction. For example, the reduction of silver ion is given by:
\[ \mathrm{Ag}^{+} + e^{-} \rightarrow \mathrm{Ag} \quad (E^{\circ} = +0.80 \, \text{V}) \]
A positive potential value suggests that reduction is favorable, making the species an excellent oxidizing agent. The higher the positive value, the greater its ability to pull electrons towards itself.

Reduction Reactions

Reduction reactions are processes where a molecule, atom, or ion gains electrons. This "gain of electrons" can be remembered with the mnemonic "OIL RIG"—Oxidation Is Loss, Reduction Is Gain. During a reduction reaction, the charge on the species is decreased, often making it more stable.
These reactions are the opposite of oxidation reactions, where electrons are lost. In the case of our example ions, - When \(\mathrm{Ag}^{+}\) gains an electron, it becomes silver metal (Ag). - Conversely, \(\mathrm{Na}^{+}\) has a significantly negative reduction potential, making it a poor oxidizing agent.
Reduction reactions are integral to many natural and industrial processes, such as energy production in batteries and metal extraction.

Electron Transfer

Electron transfer is a fundamental process in chemistry where electrons move from one atom or molecule to another. This transfer is critical in redox reactions, where one species is oxidized (loses electrons) and the other is reduced (gains electrons).In our context, the transfer depends heavily on the standard reduction potentials of the involved species:

• Species with higher (more positive) reduction potential are generally better at gaining electrons.
• Species with lower (more negative) reduction potential are better at losing electrons.

For instance, silver ion (\(\mathrm{Ag}^{+}\)) has a stronger pull for electrons compared to \(\mathrm{Na}^{+}\), as indicated by their respective potential values. Thus, \(\mathrm{Ag}^{+}\) is more likely to participate in reactions as an oxidizing agent by accepting electrons.