Problem 5 - A Complete Resource Book in Chemistry for JEE Main

Question

An example of amphoteric oxide is (a) \(\mathrm{Ti}_{2} \mathrm{O}_{2}\) (b) \(\mathrm{MgO}\) (c) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) (d) \(\mathrm{Al}_{2} \mathrm{O}_{3}\)

Step-by-Step Solution

Answer

(d) \(\mathrm{Al}_{2} \mathrm{O}_{3}\) is an amphoteric oxide.

Step 1: Understanding Amphoteric Oxides

Amphoteric oxides are oxides that can react both with acids and bases to produce salts and water. In other words, they can act as either acidic or basic oxides depending on the nature of the other reactant.

Step 2: Analyzing Given Options

We need to find out which oxide from the given options exhibits this dual behavior. (a) \(\mathrm{Ti}_{2} \mathrm{O}_{2}\): Typically, titanium oxides are not known for amphoteric behavior.(b) \(\mathrm{MgO}\): Magnesium oxide is basic and does not show amphoteric properties.(c) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\): This is a strongly acidic oxide, not amphoteric.(d) \(\mathrm{Al}_{2} \mathrm{O}_{3}\): Aluminum oxide is a well-known amphoteric oxide, reacting with both acids and bases.

Step 3: Identifying the Correct Answer

Based on the analysis, \(\mathrm{Al}_{2} \mathrm{O}_{3}\) is the only oxide among the options listed that can behave both as an acid and as a base. Thus, it is the correct choice for an amphoteric oxide.

Key Concepts

Reaction with Acids

Amphoteric oxides such as aluminum oxide (\(\mathrm{Al}_{2} \mathrm{O}_{3}\)) can react with acids. When aluminum oxide reacts with an acid, it acts as a base.
This reaction with acids leads to the formation of a salt and water.
For instance, when \(\mathrm{Al}_{2} \mathrm{O}_{3}\) is reacted with hydrochloric acid (\(\mathrm{HCl}\)), the chemical reaction can be represented as follows:

• \(\mathrm{Al}_{2} \mathrm{O}_{3} + 6 \mathrm{HCl} \rightarrow 2 \mathrm{AlCl}_{3} + 3 \mathrm{H}_{2}\mathrm{O}\)

Here, \(\mathrm{Al}_{2} \mathrm{O}_{3}\) neutralizes the \(\mathrm{HCl}\) and forms aluminum chloride (\(\mathrm{AlCl}_{3}\)), which is a salt, along with water.
It's intriguing to note that aluminum oxide's behavior changes with different reactants, enabling it to form a multitude of compounds.

Reaction with Bases

When an amphoteric oxide like aluminum oxide encounters a base, it exhibits an acidic nature. In this reaction, \(\mathrm{Al}_{2} \mathrm{O}_{3}\) reacts with a base to produce a salt and water, similar to how acids react with bases.
For example, when aluminum oxide reacts with sodium hydroxide (\(\mathrm{NaOH}\)), an important base, the reaction is:

• \(\mathrm{Al}_{2} \mathrm{O}_{3} + 2 \mathrm{NaOH} + 3 \mathrm{H}_{2}\mathrm{O} \rightarrow 2 \mathrm{NaAl(OH)}_{4}\)

This produces sodium aluminate (\(\mathrm{NaAl(OH)}_{4}\)), demonstrating the acidic property of aluminum oxide.
This dual character allows aluminum oxide to engage in versatile reactions, making it useful in various chemical processes.

Aluminum Oxide

Aluminum oxide, also known by its chemical formula \(\mathrm{Al}_{2} \mathrm{O}_{3}\), is a unique compound due to its amphoteric nature. This means it can act as both an acid and a base depending on the reaction circumstances.

• In acidic environments, it behaves like a base.


• In basic surroundings, it behaves like an acid.

This versatile behavior makes \(\mathrm{Al}_{2} \mathrm{O}_{3}\) particularly important in chemistry. You will find it used in industries involved in metals extraction, ceramics, and in the manufacture of refractories.
Its dual capacity to react brings it into a wide array of chemical contexts, thereby expanding its utility and relevance in both industrially and educationally.