Problem 20 - Chemistry in 30 days

Question

Tin reacts with conc. \(\mathrm{HNO}_{3}\) and gives (a) Stannic nitrate (b) Stannous nitrate (c) Metastannic acid (d) None of these

Step-by-Step Solution

Answer

The product formed is metastannic acid, so the answer is (c).

Step 1: Analyze the Reactants

The problem states that tin (Sn) reacts with concentrated nitric acid (NO_3). In this reaction, nitric acid acts as a strong oxidizing agent.

Step 2: Predict the Products of the Reaction

When tin reacts with concentrated nitric acid, instead of forming any simple nitrates directly, a complex reaction occurs. The tin is oxidized, and metastannic acid (H_2SnO_3 or its hydrated form) is commonly formed. Additionally, nitrogen oxides like NO_2 are released as byproducts.

Step 3: Consider the Options

The problem offers four options: (a) stannic nitrate, (b) stannous nitrate, (c) metastannic acid, and (d) none of these. Given the prediction in Step 2, metastannic acid (option c) aligns with the typical reaction products for tin with concentrated nitric acid.

Step 4: Conclusion

Based on the analysis and prediction, the product formed when tin reacts with concentrated nitric acid is metastannic acid. Therefore, the correct answer is option (c).

Key Concepts

Oxidizing Agents

In chemistry, oxidizing agents, also known as oxidants, are substances that have the ability to oxidize other substances. This means they can accept electrons from those substances. As they do this, the oxidizing agent itself is reduced.

Oxidizing agents often contain highly electronegative elements, like oxygen or fluorine, or possess the ability to stabilize additional electrons.

• Strong oxidizing agents can cause oxidation reactions to occur more rapidly.
• They are critical in many types of chemical reactions, including those that involve corrosion, combustion, and metabolic processes.

In the reaction involving tin and concentrated nitric acid, \[\text{Sn} + \text{HNO}_3 \rightarrow \text{H}_2\text{SnO}_3 + \text{NO}_2\] nitric acid acts as the oxidizing agent. It accepts electrons from tin, allowing it to form metastannic acid as a product. This transformation is key to understanding how such reactions take place in inorganic chemistry.

Metastannic Acid

Metastannic acid, with the chemical formula \( \text{H}_2\text{SnO}_3 \), is a chemical compound that is often formed as a white powdery solid in reactions involving tin. It is known for its somewhat complex polymeric structure.

Metastannic acid isn't a simple species; instead, its structure involves many tin and oxygen atoms interconnected in a network.

• This property affects its solubility in water, as it tends to form a gelatinous precipitate.
• Metastannic acid is often derived from the action of strong acids, like nitric acid, on tin metal.

This type of acid plays a significant role in industrial processes where tin reactions are necessary. Its formation typically indicates an oxidation process where tin moves from a metal to a more stable oxidized state.

Tin Reactions

Tin is a versatile metal with interesting reactive properties, especially when it interacts with different chemicals. In its metallic form, tin is fairly resistant to corrosion.

However, when exposed to oxidizing agents, like concentrated nitric acid, it can easily undergo chemical changes.

• Reactions with acids often lead to the formation of oxides or acid salts, depending on the nature of the acid used.
• For instance, with dilute \(\text{HCl}\), tin reacts to form tin chloride, while with concentrated \(\text{HNO}_3\), it forms metastannic acid.

These reactions highlight the complexity and versatility of tin chemistry. An understanding of these reactions is essential for applications ranging from metal finishing processes to the development of new chemical products.

Nitric Acid

Nitric acid \((\text{HNO}_3)\) is a powerful and widely used acid in the field of chemistry and industry. It's renowned for being a strong oxidizing agent.

Concentrated nitric acid can cause rapid oxidation in metals.

• It plays a critical role in nitrate synthesis and other industrial applications, like fertilizer and explosives manufacture.
• When handled, it emits noxious brown fumes, primarily nitrogen dioxide \((\text{NO}_2)\) , which illustrate its ability to decompose and oxidize materials around it.

During its reaction with tin, as in the presented exercise, nitric acid oxidizes tin, resulting in the formation of metastannic acid and the release of nitrogen oxides. This property is heavily leveraged in both chemical processing and academic demonstrations of oxidation reactions.