Problem 15 - Chemistry The Central Science In Si Units

Question

Indicate whether each of the following statements is true or false: (a) If something is oxidized, it is formally losing electrons. (b) For the reaction \(\mathrm{Fe}^{3+}(a q)+\mathrm{Co}^{2+}(a q) \longrightarrow \mathrm{Fe}^{2+}(a q)+\) \(\mathrm{Co}^{3+}(a q), \mathrm{Fe}^{3+}(a q)\) 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: Analyze Statement (a)

Statement (a) claims "If something is oxidized, it is formally losing electrons." To determine if this is true, recall the definition of oxidation in redox reactions. Oxidation involves the loss of electrons by a substance. Therefore, statement (a) is true.

Step 2: Analyze Statement (b)

Statement (b) describes a reaction: \( \mathrm{Fe}^{3+}(a q)+\mathrm{Co}^{2+}(a q) \longrightarrow \mathrm{Fe}^{2+}(a q)+ \mathrm{Co}^{3+}(a q) \). Let's determine the roles of the agents. \( \mathrm{Fe}^{3+} \) is reduced to \( \mathrm{Fe}^{2+} \), implying it gains electrons (thus it is an oxidizing agent). \( \mathrm{Co}^{2+} \) is oxidized to \( \mathrm{Co}^{3+} \), meaning it loses electrons, acting as a reducing agent. Therefore, statement (b) is false.

Step 3: Analyze Statement (c)

Statement (c) says "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." A redox reaction is characterized by the change in oxidation states of the reactants. If no changes occur, then it is not a redox reaction. Hence, statement (c) is true.

Key Concepts

Oxidation

Oxidation is a fundamental concept in redox reactions. In simple terms, oxidation involves the loss of electrons from a substance. This process leads to an increase in the oxidation state of the element that is oxidized.
For example, when a metal reacts with oxygen, the metal loses electrons and is oxidized to form a metal oxide. It's helpful to remember oxidation using the acronym OIL RIG: "Oxidation is Loss" (of electrons), which complements the idea of reduction, where "Reduction is Gain" (of electrons). In any redox reaction, if one substance is oxidized, another must be reduced simultaneously, making them inseparable processes. In practice, when trying to identify if an oxidation has occurred, watch for certain chemical changes:

• Increase in oxidation state (numerical value)
• Loss of electrons
• Often involves gaining oxygen or losing hydrogen

Reducing Agent

A reducing agent plays a crucial role by donating electrons to another substance. This agent undergoes oxidation itself, as it sacrifices its electrons for the reduction of another substance.
In redox reactions, the reducing agent is responsible for causing the reduction of the other reactant. In the common reaction between iron and cobalt ions: \[ \mathrm{Fe}^{3+}(aq) + \mathrm{Co}^{2+}(aq) \rightarrow \mathrm{Fe}^{2+}(aq) + \mathrm{Co}^{3+}(aq) \]\(\mathrm{Co}^{2+}\) is the reducing agent. As it loses an electron to become \(\mathrm{Co}^{3+}\), it facilitates the gain of electrons by iron, making itself oxidized.
To remember the function of reducing agents, consider these points:

• Reducing agents have atoms that lose electrons
• They are oxidized in the process
• Commonly possess elements that have low electronegativity

Oxidizing Agent

The oxidizing agent is essentially the opposite of the reducing agent in a redox reaction. It is responsible for oxidizing another substance by accepting electrons from it. During this process, the oxidizing agent itself is reduced.
In general, oxidizing agents help drive the redox reaction by pulling electrons away from the reducing agent.In the reaction involving iron and cobalt ions, mentioned earlier:\[ \mathrm{Fe}^{3+}(aq) + \mathrm{Co}^{2+}(aq) \rightarrow \mathrm{Fe}^{2+}(aq) + \mathrm{Co}^{3+}(aq) \]\(\mathrm{Fe}^{3+}\) acts as the oxidizing agent. It accepts an electron to become \(\mathrm{Fe}^{2+}\), while \(\mathrm{Co}^{2+}\) loses its electrons.
Here are some key characteristics of oxidizing agents:

• They accept electrons and are reduced
• Often involve non-metals or elements with high electronegativity
• Commonly associated with gaining oxygen or losing hydrogen