Problem 4 - Chemistry A Guided Inquiry

Question

Is a species that has an atom for which there is an increase in oxidation number oxidized or reduced? Is that species the oxidizing agent or the reducing agent?

Step-by-Step Solution

Answer

The species in question, which has an increase in oxidation number, is oxidised and acts as the reducing agent.

Step 1: Understand Oxidation and Reduction

The terms 'oxidation' and 'reduction' refer to processes where there is a change in the number of electrons an atom has. If an atom loses electrons, it's said to be oxidized. If it gains electrons, it's reduced. Hence, a species that has an increase in oxidation number is being oxidized, as it is losing electrons.

Step 2: Understand Reducing and Oxidizing Agents

A reducing agent loses electrons and is oxidised, while an oxidizing agent gains electrons and is reduced. Since our species is being oxidized, it is losing electrons and therefore it is behaving as a reducing agent.

Key Concepts

Oxidation Number

The oxidation number of an atom in a molecule or ion is a helpful bookkeeping tool that allows us to keep track of electrons during a chemical reaction. It essentially indicates the degree of oxidation of an atom.

• When an atom loses electrons, the oxidation number increases; this indicates oxidation.
• Conversely, a decrease in oxidation number signifies that an atom has gained electrons, suggesting reduction.

Understanding how oxidation numbers change during reactions can help identify which species are oxidized and which are reduced. This is crucial for balancing redox reactions, where both oxidation and reduction occur, maintaining the conservation of charge and mass.

Oxidizing Agent

An oxidizing agent, or oxidant, is a substance that promotes oxidation by gaining electrons. It undergoes a reduction itself in the process.

• Think of it like this: an oxidizing agent 'oxidizes' another substance by taking electrons away from it.
• As it accepts electrons, its own oxidation number decreases.

Identifying the oxidizing agent in a reaction helps in understanding the flow of electrons and the direction of the chemical change. In the exercise example, the species that gains electrons and experiences a reduction acts as the oxidizing agent.

Reducing Agent

A reducing agent, or reductant, is a substance that causes another chemical to be reduced by donating electrons to it. Thus, the reducing agent itself undergoes oxidation.

• In simple terms, think of the reducing agent as the donor of electrons; it 'reduces' another species by giving away electrons.
• This leads to an increase in its oxidation number as it loses electrons.

Understanding the role of the reducing agent helps clarify which parts of a chemical reaction are donating electrons, and how the balance of electron transfer maintains reactants and products. In our exercise solution, the species with the increase in oxidation number acts as the reducing agent, donating electrons to another species.