Problem 11 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The acidic, basic and amphoteric oxides, respectively, are: (a) \(\mathrm{Na}_{2} \mathrm{O}, \mathrm{SO}_{3}, \mathrm{Al}_{2} \mathrm{O}_{3}\) (b) \(\mathrm{Cl}_{2} \mathrm{O}, \mathrm{CaO}, \mathrm{P}_{4} \mathrm{O}_{10}\) (c) \(\mathrm{N}_{2} \mathrm{O}_{3}, \mathrm{Li}_{2} \mathrm{O}, \mathrm{Al}_{2} \mathrm{O}_{3}\) (d) \(\mathrm{MgO}, \mathrm{Cl}_{2} \mathrm{O}, \mathrm{Al}_{2} \mathrm{O}_{3}\)

Step-by-Step Solution

Answer

The correct answer is (c).

Step 1: Definition of Acidic Oxides

Acidic oxides are oxides that react with water to form an acid or react with a base to form a salt. Examples include oxides of nonmetals such as \(\mathrm{SO}_3\) which forms sulfuric acid when combined with water.

Step 2: Identifying Basic Oxides

Basic oxides are oxides that react with water to form a base or react with an acid to form a salt. Metallic oxides like \(\mathrm{Na}_2\mathrm{O}\) (sodium oxide) or \(\mathrm{CaO}\) (calcium oxide) are common examples.

Step 3: Recognizing Amphoteric Oxides

Amphoteric oxides have both acidic and basic properties. They can react with both acids and bases to form salts and water. \(\mathrm{Al}_2\mathrm{O}_3\) (aluminum oxide) is a classic example of an amphoteric oxide.

Step 4: Analyzing Each Option

Evaluate each choice based on the definitions of acidic, basic, and amphoteric oxides. Check which triad fulfills the requirement of one of each type: \(\mathrm{Na}_2\mathrm{O}\) (basic), \(\mathrm{SO}_3\) (acidic), and \(\mathrm{Al}_2\mathrm{O}_3\) (amphoteric) in option (a); \(\mathrm{Cl}_2\mathrm{O}\) (acidic), \(\mathrm{CaO}\) (basic), \(\mathrm{P}_4\mathrm{O}_{10}\) (acidic) in option (b); \(\mathrm{N}_2\mathrm{O}_3\) (acidic), \(\mathrm{Li}_2\mathrm{O}\) (basic), \(\mathrm{Al}_2\mathrm{O}_3\) (amphoteric) in option (c); \(\mathrm{MgO}\) (basic), \(\mathrm{Cl}_2\mathrm{O}\) (acidic), \(\mathrm{Al}_2\mathrm{O}_3\) (amphoteric) in option (d).

Step 5: Verify the Correct Answer

After analyzing all options, check which group has all three types: an acidic, a basic, and an amphoteric oxide. Option (c) has \(\mathrm{N}_2\mathrm{O}_3\) as acidic, \(\mathrm{Li}_2\mathrm{O}\) as basic, and \(\mathrm{Al}_2\mathrm{O}_3\) as amphoteric, making it the correct choice.

Key Concepts

Basic Oxides

Basic oxides are fascinating substances primarily formed from the reaction of metals with oxygen. These oxides have the distinctive feature of being able to react with water to yield a base, commonly known as an alkali, or neutralize an acid to form a salt.
One well-known example is sodium oxide (\(\mathrm{Na}_2\mathrm{O}\)). When sodium oxide reacts with water, it produces sodium hydroxide (\(\mathrm{NaOH}\)), a strong base.

• \(\mathrm{Na}_2\mathrm{O} + \mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{NaOH}\)

Another classic example is calcium oxide (\(\mathrm{CaO}\)), which reacts with water to form calcium hydroxide (\(\mathrm{Ca(OH)_2}\)):

• \(\mathrm{CaO} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{Ca(OH)_2}\)

Typically, basic oxides originate from Group 1 and Group 2 elements in the periodic table, often composed of alkali and alkaline earth metals.
This property makes them crucial for various industrial applications, like in the production of building materials and as lubricants in small quantities.

Amphoteric Oxides

Amphoteric oxides are versatile chemical compounds that can exhibit both basic and acidic characteristics. This unique property allows them to react with both acids and bases to form salts and water.
A quintessential example is aluminum oxide (\(\mathrm{Al}_2\mathrm{O}_3\)). In acidic solutions, such as hydrochloric acid, aluminum oxide acts as a base:

• \(\mathrm{Al}_2\mathrm{O}_3 + 6\mathrm{HCl} \rightarrow 2\mathrm{AlCl}_3 + 3\mathrm{H}_2\mathrm{O}\)

Conversely, in basic solutions like sodium hydroxide, it behaves as an acid:

• \(\mathrm{Al}_2\mathrm{O}_3 + 2\mathrm{NaOH} + 3\mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{NaAl(OH)_4}\)

Amphoteric oxides are particularly interesting in metallurgy and materials chemistry. For example, the property of \(\mathrm{Al}_2\mathrm{O}_3\) is significant in the extraction and refining of aluminum metal.
This characteristic can also be utilized in wastewater treatment and other industrial processes where neutralization reactions are needed.

Chemical Reactions with Water

Chemical reactions involving water are fundamental in understanding the nature of oxides and their behavior in different conditions. These reactions vary according to whether the oxide is acidic, basic, or amphoteric.
When we talk about basic oxides, their reaction with water generally results in the formation of hydroxides. Such aqueous reactions are often exothermic, meaning they release heat. For example, when calcium oxide reacts with water, calcium hydroxide is produced along with heat:

• \(\mathrm{CaO} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{Ca(OH)_2}\)

Meanwhile, acidic oxides, mainly non-metallic oxides, form acids when they come into contact with water. A classic example includes sulfur trioxide (\(\mathrm{SO}_3\)) which reacts with water to form sulfuric acid (\(\mathrm{H}_2\mathrm{SO}_4\)):

• \(\mathrm{SO}_3 + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}_2\mathrm{SO}_4\)

Understanding these reactions helps in predicting the behavior of oxides in natural and industrial environments.
This knowledge is critical, among others, in areas like environmental science, where the formation of acid rain is considered.