Problem 10 - Chemistry in 30 days

Question

Which of the following on thermal decomposition yields a basic as well as an acidic oxide? (a) \(\mathrm{KClO}_{3}\) (b) \(\mathrm{CaCO}_{3}\) (c) \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) (d) \(\mathrm{NaNO}_{3}\)

Step-by-Step Solution

Answer

Option (b) \( \mathrm{CaCO}_{3} \) yields a basic and an acidic oxide upon decomposition.

Step 1: Analyze Thermal Decomposition

Let's examine each option one by one for thermal decomposition. During thermal decomposition, compounds break down into simpler substances such as metals, gases, and oxides.

Step 2: Determine Decomposition Products of KClO3

When \( \mathrm{KClO}_{3} \) decomposes, it breaks down into potassium chloride (\( \mathrm{KCl} \)) and oxygen (\( \mathrm{O}_{2} \)). This does not produce an acidic or basic oxide.

Step 3: Evaluate Decomposition of CaCO3

Calcium carbonate (\( \mathrm{CaCO}_{3} \)) decomposes to form calcium oxide (\( \mathrm{CaO} \)) and carbon dioxide (\( \mathrm{CO}_{2} \)). Calcium oxide is a basic oxide and carbon dioxide is an acidic oxide.

Step 4: Analyze NH4NO3 Decomposition

Upon heating, \( \mathrm{NH}_{4} \mathrm{NO}_{3} \) decomposes to form nitrous oxide (\( \mathrm{N}_{2}\mathrm{O} \)) and water (\( \mathrm{H}_{2}\mathrm{O} \)). It does not produce an acidic or basic oxide.

Step 5: Examine NaNO3 Decomposition

Sodium nitrate (\( \mathrm{NaNO}_{3} \)) decomposes into sodium nitrite (\( \mathrm{NaNO}_{2} \)) and oxygen (\( \mathrm{O}_{2} \)). This does not yield an acidic or basic oxide.

Step 6: Conclusion

Only \( \mathrm{CaCO}_{3} \) decomposes to form a basic and an acidic oxide. Calcium oxide (basic) and carbon dioxide (acidic) are produced.

Key Concepts

Calcium Carbonate

Calcium carbonate, represented chemically as \( \mathrm{CaCO}_{3} \), is an important compound commonly found in rocks and minerals such as limestone and marble. It's used in various industries, such as construction and manufacturing. When subjected to heat, it undergoes thermal decomposition, a chemical process where a compound breaks down into simpler products. In the case of calcium carbonate, upon heating, it decomposes into calcium oxide (\( \mathrm{CaO} \)) and carbon dioxide (\( \mathrm{CO}_{2} \)).

• Calcium oxide is a solid and is often referred to as quicklime.
• Carbon dioxide is a gas, which is released into the atmosphere during the decomposition process.

This decomposition is significant in processes such as the manufacture of cement and lime, which are crucial for infrastructure and industrial applications.

Basic Oxide

A basic oxide is formed when metals react with oxygen. It typically contains oxygen bonded to a metal and generally reacts with acids to form salts and water. Calcium oxide (\( \mathrm{CaO} \)), a product of calcium carbonate decomposition, is a classic example. It exhibits characteristics typical of basic oxides, including:

• It reacts readily with water to form calcium hydroxide, a process known as slaking.
• It reacts with acids to produce salt and water, displaying its basic nature.

Basic oxides are instrumental in neutralizing acidic environments, necessary in various industrial and environmental processes, such as waste treatment and soil pH management.

Acidic Oxide

Acidic oxides are typically non-metal oxides that react with bases to form salt and water. Carbon dioxide (\( \mathrm{CO}_{2} \)), produced from the decomposition of calcium carbonate, is a quintessential acidic oxide. Here are some features and behaviors of acidic oxides:

• When dissolved in water, carbon dioxide forms carbonic acid, which indicates it has acidic properties.
• It reacts with basic substances like calcium hydroxide to form calcium carbonate and water.

Understanding acidic oxides is vital because they are significant contributors to various natural processes and environmental phenomena, helping explain interactions like acid rain and certain biological systems.

Chemical Reactions

Chemical reactions involve the rearrangement of atoms or ions into different substances. Thermal decomposition is a specific type of chemical reaction where heat causes compounds to break down into simpler components. In the context of calcium carbonate, the equation \[ \mathrm{CaCO}_{3} \rightarrow \mathrm{CaO} + \mathrm{CO}_{2}\]illustrates its decomposition into calcium oxide and carbon dioxide. This is a thermal decomposition reaction because it requires heat to proceed. Such reactions are critical in the industrial sector, especially in producing commodities like lime and cement. Comprehensive understanding of these reactions helps in advancing material production, waste management, and environmental conservation. By mastering these concepts, we better grasp how elements and compounds behave under different conditions.