Problem 201 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following oxides is amphoteric in character? (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{SiO}_{2}\) (c) \(\mathrm{SnO}_{2}\) (d) \(\mathrm{CaO}\)

Step-by-Step Solution

Answer

\(\mathrm{SnO}_{2}\) is the amphoteric oxide.

Step 1: Define Amphoteric Oxide

An amphoteric oxide is one that can react both with acids and bases to form salts and water. This dual nature of reacting with both gives it unique properties compared to regular acidic or basic oxides.

Step 2: Analyze Each Option

Review the given options to determine whether they can react with both acids and bases:- \(\mathrm{CO}_{2}\) is typically acidic, reacting with bases.- \(\mathrm{SiO}_{2}\) is a weak acid and reacts with strong bases.- \(\mathrm{SnO}_{2}\) can react with both acids and bases.- \(\mathrm{CaO}\) is a basic oxide and reacts with acids.

Step 3: Selecting the Amphoteric Oxide

Given the ability to react with both acids and bases, \(\mathrm{SnO}_{2}\) is classified as an amphoteric oxide.

Key Concepts

Characteristics of Oxides

Oxides are chemical compounds that contain at least one oxygen atom and one other element in their chemical formula. They are classified based on the nature and behavior of their reaction with other substances. The primary types of oxides include acidic oxides, basic oxides, and amphoteric oxides.

The characteristics of oxides are largely influenced by the elements they are combined with and their ability to form certain bonds.

• **Acidic Oxides**: Generally associated with non-metals, acidic oxides can react with water to form acids. For example, \(\mathrm{CO}_{2}\) reacts with water to produce carbonic acid.
• **Basic Oxides**: Usually derived from metals, these oxides react with acids to form salts and water. A typical example is \(\mathrm{CaO}\), which reacts with \(\mathrm{HCl}\) to form \(\mathrm{CaCl}_{2}\) and water.
• **Amphoteric Oxides**: These possess the unique characteristic of reacting with both acids and bases, making them very versatile. A key example is \(\mathrm{SnO}_{2}\), which can form different products depending on whether it reacts with an acid or a base.

Understanding these characteristics is fundamental as they determine how oxides will interact in various chemical reactions. This knowledge is crucial in predicting the behavior of oxides in industrial and laboratory processes.

Reactivity with Acids and Bases

The reactivity of oxides with acids and bases is a defining property that is used to distinguish between their different categories.

**Amphoteric Oxides** like \(\mathrm{SnO}_{2}\) demonstrate their ability to react uniquely with both acids and bases:

• When reacting with acids, such as \(\mathrm{HCl}\), \(\mathrm{SnO}_{2}\) forms tin chlorides, releasing water as a byproduct.
• Conversely, when reacting with a base like sodium hydroxide (\(\mathrm{NaOH}\)), it can form complex compounds such as sodium stannate, again often releasing water.

This dual reactivity is the signature characteristic of amphoteric oxides, allowing them to participate in diverse chemical processes.

**Acidic Oxides** react predominantly with bases. Take \(\mathrm{CO}_{2}\), for example. This oxide will typically react with \(\mathrm{NaOH}\) to form sodium carbonate, demonstrating its acidic nature.**Basic Oxides**, on the other hand, react with acids. A classic reaction is that of \(\mathrm{CaO}\) with hydrochloric acid, forming calcium chloride and water. Understanding the reactivity patterns of these oxides helps in foreseeing the outcomes of chemical reactions and their potential uses in various industries.

Classification of Oxides

The classification of oxides is an essential concept in chemistry, providing insights into the nature and behavior of compounds. Chemists classify oxides based on how they react with acids and bases.

• **Acidic Oxides**: Formed with non-metals, they react with bases to form salt and water. Examples include \(\mathrm{CO}_{2}\) and \(\mathrm{SO}_{2}\).
• **Basic Oxides**: Produced by metals, basic oxides dissolve in acids to form corresponding salts and water. Some common examples are \(\mathrm{CaO}\) and \(\mathrm{Na}_{2}\mathrm{O}\).
• **Amphoteric Oxides**: As mentioned, these can react with both acids and bases. \(\mathrm{SnO}_{2}\) is a great example of such oxides.
• **Neutral Oxides**: A less common type, they usually do not react with either acids or bases, such as \(\mathrm{N}_{2}\mathrm{O}\) and \(\mathrm{CO}\).

Understanding the classification of oxides helps predict how they'll behave in chemical reactions. This is particularly useful in industrial applications and for students learning about chemical processes. Identifying the type of oxide can allow scientists and students to make predictions about its reactivity and the kind of products it will form in reactions.