Discuss the oxidising action of dilute and conc. nitric acid with the help of suitable examples.

Nitric acid (NO_{3}(aq)) is a versatile substance that plays a significant role in the field of chemistry. It acts as a powerful oxidizing agent capable of transforming metals and non-metals into their respective oxidized forms. Chemically, nitric acid tends to give away its nitrogen-oxygen part to the reacting substance, effectively increasing the oxidation state of that substance. This process is critical in various industrial applications, such as in the production of fertilizers, explosives, and in metal processing.

When nitric acid reacts with different substances, it also undergoes changes. For example, the oxidation state of nitrogen in nitric acid may decrease, forming different nitrogen oxides such as nitric oxide (NO(g)) or nitrogen dioxide (NO_{2}(g)) depending on its concentration and the conditions of the reaction. Understanding the chemical behavior of nitric acid not only aids in following safety protocols in its handling but also enriches the knowledge of chemical synthesis in both academic and industrial settings.

Oxidation states, often referred to as oxidation numbers, play a pivotal role in understanding chemical reactions, particularly redox reactions where oxidation and reduction occur simultaneously. The concept of oxidation states helps in tracking the transfer of electrons in a reaction, allowing chemists to balance chemical equations and predict the formation of products.

For instance, copper in its elemental form has an oxidation state of 0. When it reacts with nitric acid, its oxidation state escalates to +2 in the resulting copper nitrate (Cu(NO_{3})_{2}(aq)), signifying loss of electrons or oxidation. Conversely, the nitrogen within nitric acid, originally at an oxidation state of +5, decreases to +2 or +4 in nitric oxide (NO(g)) or nitrogen dioxide (NO_{2}(g)), respectively, showing it was reduced. Mastery of oxidation states ensures not only excellent grasp of redox principles but also safe and effective experimental designs.

The interaction between copper and nitric acid is a classic example of a redox reaction, showcasing the variance in nitric acid's oxidizing power based on its concentration. When copper (Cu(s)) reacts with dilute nitric acid, it yields copper nitrate, water (H_{2}O_{(l)}), and nitric oxide (NO_{2}(g)), a process accompanied by the characteristic blue coloration of the resulting solution indicating the presence of copper ions.

Variations in Reactions with Concentration

If the nitric acid is concentrated, the nitrogen dioxide (NO_{2}(g)) produced often presents a brownish-red gas, signifying a stronger oxidizing action and a change in the nitrogen oxide formed. This reaction provides a vivid demonstration of chemical principles, useful in various analytical and synthesis processes in chemistry. Learning about such reactions not only furthers academic understanding but also emphasizes the safety and precision needed in handling substances with varying hazardous potentials.