Question

Explain why nitric acid can be reduced but not oxidized.

Short answer

Nitric acid can be reduced due to its high nitrogen oxidation state, but it can't be oxidized further.

Step-by-step solution

Understand Oxidation and Reduction

Oxidation is the loss of electrons, whereas reduction is the gain of electrons. An oxidizing agent gains electrons and gets reduced, while a reducing agent loses electrons and gets oxidized.

Analyze the Chemical Structure of Nitric Acid

Nitric acid (HNO₃) contains nitrogen. In its structure, nitrogen is already in a high oxidation state (+5). This means it has accepted as many electrons as it can and cannot easily lose more electrons to be oxidized further.

Explain Why Nitric Acid Can Be Reduced

Since nitrogen is in a high oxidation state in nitric acid, it can gain electrons, which means it can be reduced. Reduction of nitric acid results in the formation of nitrogen oxides or ammonia, where nitrogen has a lower oxidation state.

Conclude Why Nitric Acid Can't Be Oxidized

Because the nitrogen in nitric acid is at its maximum oxidation state, nitric acid cannot lose electrons further to become oxidized.

Key concepts

Oxidation State

The oxidation state is a number assigned to an element in a compound, signifying its degree of oxidation or reduction. Essentially, it indicates the number of electrons an atom can gain, lose, or share in a chemical reaction.
This is crucial for understanding how different substances can interact during reactions. For example, in nitric acid (HNO₃), nitrogen has an oxidation state of +5.
This high oxidation state arises because nitrogen has essentially "given up" five electrons when bonded in this compound. Determining the oxidation states of different elements helps predict how they might react. They indicate whether a substance can act as an oxidizing agent or not.

Oxidation and Reduction

In chemistry, oxidation and reduction are two complementary processes. Oxidation involves the loss of electrons, whereas reduction involves the gain of electrons.
Together, these processes are called redox reactions. These types of reactions are vital for numerous biological and industrial processes. - **Oxidation** – Loses electrons, resulting in an increase in oxidation state. - **Reduction** – Gains electrons, resulting in a decrease in oxidation state. Understanding these processes helps explain how substances like nitric acid react. In its reactions, nitric acid acts as an oxidizing agent, readily gaining electrons to become reduced. This interaction is central for nitric acid's role in chemical reactions.

Chemical Structure

The chemical structure of a compound is an arrangement of its atoms that determines its properties and reactivity. Knowing the structure helps in understanding the behavior of a substance in reactions.
Nitric acid (HNO₃) consists of hydrogen, nitrogen, and three oxygen atoms. The nitrogen atom in this compound is in a +5 oxidation state, which means it's surrounded by highly electronegative oxygen atoms.
This particular structure is why nitric acid can act as a strong oxidizing agent, eager to accept electrons and reduce itself. This configuration illustrates why nitrogen in HNO₃ cannot be oxidized any further, as it already shares the maximum number of electrons with oxygen.

Oxidizing Agent

An oxidizing agent is a substance that brings about oxidation by accepting electrons from other substances.
In simple terms, it gets reduced while causing another substance to be oxidized. Good oxidizing agents have elements in high oxidation states, making them eager to gain electrons.

• Oxidizing agents are often oxygen, halogens, or compounds like nitric acid (HNO₃).
• They play crucial roles in both synthetic and natural chemical processes.

For nitric acid, its role as an oxidizing agent stems from the high oxidation state of nitrogen (+5).
This means that nitric acid will preferentially undergo reduction by gaining electrons, while causing other substances in the chemical reaction to oxidize. Understanding this principle clarifies why nitric acid can be reduced but not oxidized.