Question

Classify these following oxides as acidic, basic, amphoteric, or neutral: (a) \(\mathrm{CO}_{2},\) (b) \(\mathrm{K}_{2} \mathrm{O},\) (c) \(\mathrm{CaO}\) (d) \(\mathrm{N}_{2} \mathrm{O}_{5},(\mathrm{e}) \mathrm{CO},(\mathrm{f}) \mathrm{NO}\) \((\mathrm{g}) \mathrm{SnO}_{2},(\mathrm{~h}) \mathrm{SO}_{3},(\mathrm{i}) \mathrm{Al}_{2} \mathrm{O}_{3}\) (j) \(\mathrm{BaO}\).

Short answer

CO2 and N2O5 are acidic oxides. K2O, CaO and BaO are basic oxides. CO and NO are neutral oxides. SnO2 and Al2O3 are amphoteric oxides.

Step-by-step solution

Classify CO2

Carbon Dioxide (CO2) reacts with water to form carbonic acid (H2CO3). So, CO2 is an acidic oxide.

Classify K2O

Potassium oxide (K2O) reacts with water to form a potassium hydroxide (KOH), a base. So, K2O is a basic oxide.

Classify CaO

Calcium oxide (CaO) reacts with water to form calcium hydroxide (Ca(OH)2), a base. So, CaO is a basic oxide.

Classify N2O5

Dinitrogen pentoxide (N2O5) reacts with water to form nitric acid (HNO3). So, N2O5 is an acidic oxide.

Classify CO

While Carbon Monoxide (CO) does not react with water, it reacts with acids and bases, hence, CO could be considered as a neutral oxide.

Classify NO

Nitric oxide (NO) is a neutral oxide as it shows neither basic nor acidic characteristics and doesn't react with water.

Classify SnO2

Tin dioxide (SnO2) reacts with both acids and bases. So, SnO2 is an amphoteric oxide.

Classify SO3

Sulphur trioxide (SO3) reacts with water to form sulfuric acid (H2SO4). So, SO3 is an acidic oxide.

Classify Al2O3

Aluminium oxide (Al2O3) reacts with both acids and bases. So, Al2O3 is an amphoteric oxide.

Classify BaO

Barium oxide (BaO) reacts with water to form barium hydroxide (Ba(OH)2), a base. So, BaO is a basic oxide.

Key concepts

Acidic Oxides

Acidic oxides are compounds that combine with water to produce an acid. They are typically formed from non-metal elements. For example, when carbon dioxide (CO2) comes into contact with water, it forms carbonic acid (H2CO3), making CO2 an acidic oxide. Another example is sulfur trioxide (SO3), which reacts with water to form sulfuric acid (H2SO4). Understanding acidic oxides is important because they often play significant roles in environmental processes like acid rain formation.

Properties of Acidic Oxides

• React with water to form acids.
• Form salt and water when reacted with bases.
• Are often gases at room temperature.

Basic Oxides

Basic oxides, also known as alkaline oxides, react with water to yield a base. They are generally composed of a metal combined with oxygen. A good representation of a basic oxide is potassium oxide (K2O), which forms potassium hydroxide (KOH) upon reaction with water. The same is true for calcium oxide (CaO) and barium oxide (BaO), which form their respective hydroxides, making them both basic oxides.

Notable Characteristics of Basic Oxides

• React with water to produce bases.
• React with acids to form salt and water, a reaction known as neutralization.
• Are often solid at room temperature.

Amphoteric Oxides

Amphoteric oxides are a fascinating group because they exhibit dual behavior – they can react with both acids and bases to produce salts and water. This duality makes them particularly interesting for chemists. Examples include aluminum oxide (Al2O3) and tin dioxide (SnO2). These compounds can react with hydrochloric acid to produce aluminum chloride or stannic chloride, and similarly with sodium hydroxide to form sodium aluminate or sodium stannate.

Distinguishing Features of Amphoteric Oxides

• React with both acids and bases.
• Capable of forming different types of salts.
• Typically found in metal oxides of elements near the metalloid line in the periodic table.

Neutral Oxides

Neutral oxides are quite unique because they do not exhibit any acidic or basic properties. They don’t form acids or bases in water and don't react with acids or bases. Examples of neutral oxides include nitric oxide (NO) and carbon monoxide (CO). Their reluctance to react makes them stand apart from the other types of oxides in chemistry.

Key Traits of Neutral Oxides

• Do not form acids or bases in water.
• Lack reactivity with acids and bases.
• Are typically gases like nitric oxide or carbon monoxide.

Understanding these four categories of oxides helps students predict and explain the behavior of different compounds in chemical reactions. It serves as a foundational concept for studying acid-base chemistry, environmental science, and materials science.