Problem 15 - Chemistry: The Central Science

Question

Indicate whether each of the following statements is true or false: (a) If something is axidized, it is formally losing electrons. (b) For the reaction \(\mathrm{Fe}^{3+}(a q)+\mathrm{Co}^{2+}(a q) \rightarrow \mathrm{Fe}^{2+}(a q)+\) \(\mathrm{Co}^{3+}(a q), \mathrm{Fe}^{3+}(a q)\) is the reducing agent and \(\mathrm{Co}^{2+}(a q)\) is the oxidizing agent. (c) If there are no changes in the oxidation state of the reactants or products of a particular reaction, that reaction is not a redox reaction.

Step-by-Step Solution

Answer

(a) True (b) False (c) True

Step 1: Statement (a)

If something is oxidized, it is formally losing electrons. In redox reactions, one reactant is oxidized while the other is reduced. Oxidation is defined as the process of losing electrons. Therefore, this statement is true.

Step 2: Answer to statement (a)

True.

Step 3: Statement (b)

For the reaction \(\mathrm{Fe}^{3+}(a q)+\mathrm{Co}^{2+}(a q) \rightarrow \mathrm{Fe}^{2+}(a q)+\mathrm{Co}^{3+}(a q),\) \(\mathrm{Fe}^{3+}(a q)\) is the reducing agent and \(\mathrm{Co}^{2+}(a q)\) is the oxidizing agent. To determine whether the statement is true or false, let's first examine the given reaction: \(\mathrm{Fe}^{3+}(a q)+\mathrm{Co}^{2+}(a q) \rightarrow \mathrm{Fe}^{2+}(a q)+\mathrm{Co}^{3+}(a q)\) Notice that the oxidation state of Fe changes from +3 to +2 (reduced by gaining an electron), and the oxidation state of Co changes from +2 to +3 (oxidized by losing an electron). The specie that is reduced (gains electrons) is the oxidizing agent, and the specie that is oxidized (loses electrons) is the reducing agent. Therefore, the correct statement should be: \(\mathrm{Fe}^{3+}(a q)\) is the oxidizing agent and \(\mathrm{Co}^{2+}(a q)\) is the reducing agent.

Step 4: Answer to statement (b)

False.

Step 5: Statement (c)

If there are no changes in the oxidation state of the reactants or products of a particular reaction, that reaction is not a redox reaction. Redox reactions are characterized by changes in the oxidation states of the atoms involved. If there are no changes in the oxidation states, the reaction is not a redox reaction.

Step 6: Answer to statement (c)

True. In summary: (a) True (b) False (c) True

Key Concepts

Oxidation and Reduction

Oxidation and reduction are two key mechanisms that work together in redox reactions. When a substance is oxidized, it means it loses electrons.
On the other hand, reduction involves the gain of electrons. This concept can be remembered by the mnemonic 'OIL RIG' which stands for 'Oxidation Is Loss, Reduction Is Gain'.
In any given redox reaction, these two processes occur simultaneously: one substance donates electrons while the other gains them.

• Oxidation implies an increase in oxidation state.
• Reduction implies a decrease in oxidation state.

Recognizing these processes is fundamental to understanding how substances interact in redox chemistry.

Oxidizing Agents

In a redox reaction, the oxidizing agent plays a special role. This is the substance that gains electrons, thereby causing another substance to be oxidized.
Since it gains electrons, it is said to be reduced during the reaction.
For example, in the given reaction, \(\mathrm{Fe}^{3+}(aq)\) is the oxidizing agent because it accepts electrons from \(\mathrm{Co}^{2+}(aq)\).

• Oxidizing agents facilitate the oxidation of another substance.
• They themselves are reduced in the process.

Understanding the role of oxidizing agents helps in identifying which substances will gain electrons and how the reaction dynamics work.

Reducing Agents

Reducing agents are vital in redox reactions as they donate electrons to another substance, causing it to be reduced. During this process, the reducing agent itself becomes oxidized.
This means it loses electrons.
In the exercise example, \(\mathrm{Co}^{2+}(aq)\) acts as the reducing agent as it donates electrons to \(\mathrm{Fe}^{3+}(aq)\).

• Reducing agents are electron donors.
• They enable the reduction of another substance while being oxidized themselves.

Identifying the reducing agent in a redox reaction is crucial since it highlights which substance is the electron supplier.

Oxidation States

Oxidation states (or oxidation numbers) provide a way to keep track of electrons in various elements in a chemical reaction.
They are assigned to atoms based on a set of rules and reflect the degree of oxidation of an atom.
An increase in oxidation state indicates oxidation, while a decrease indicates reduction. For the example reaction, the change in oxidation states is key to understanding the process. \(\mathrm{Fe}^{3+} \, \rightarrow \, \mathrm{Fe}^{2+}\) shows a reduction, and \(\mathrm{Co}^{2+} \, \rightarrow \, \mathrm{Co}^{3+}\) shows oxidation.

• Oxidation states help identify electron transfer during reactions.
• A higher oxidation state indicates a loss of electrons (oxidation).
• A lower oxidation state indicates a gain of electrons (reduction).

Mastery of oxidation states allows for a clearer understanding of how electrons move within redox reactions.