Problem 7 - Chemistry in 30 days

Question

On heating sodium carbonate is evolved. (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{CO}\) (c) \(\mathrm{H}_{2} \mathrm{O}\) (d) No gas

Step-by-Step Solution

Answer

(a) \( \mathrm{CO}_2 \) is evolved.

Step 1: Identify the compound

The compound in question is sodium carbonate, which has the chemical formula \( \mathrm{Na}_2\mathrm{CO}_3 \).

Step 2: Consider the decomposition reaction

On heating, sodium carbonate can decompose. The typical decomposition of \( \mathrm{Na}_2\mathrm{CO}_3 \) is as follows: \[ \mathrm{Na}_2\mathrm{CO}_3 (s) \rightarrow \mathrm{Na}_2\mathrm{O} (s) + \mathrm{CO}_2 (g) \]

Step 3: Identify the evolved gas

From the decomposition reaction, we see that \( \mathrm{CO}_2 \), which is carbon dioxide, is evolved as a gas upon heating sodium carbonate.

Key Concepts

Sodium Carbonate

Sodium carbonate, often known by its chemical formula \( \mathrm{Na}_2\mathrm{CO}_3 \), is a white, crystalline compound that's largely used in numerous industrial applications such as glass manufacturing and as a cleaning agent. It's commonly referred to as soda ash or washing soda. Sodium carbonate is quite soluble in water, forming an alkaline solution. This property makes it useful in softening water, as it can precipitate out calcium and magnesium ions. Understanding sodium carbonate is crucial because it undergoes interesting reactions when exposed to heat, which brings us to thermal decomposition.

Carbon Dioxide

Carbon dioxide, denoted chemically as \( \mathrm{CO}_2 \), is a colorless and odorless gas prominent in Earth's atmosphere. It's essential for life processes such as photosynthesis in plants and is a significant greenhouse gas influencing global temperatures. When sodium carbonate undergoes heat, it decomposes and one of the byproducts is carbon dioxide. This release of \( \mathrm{CO}_2 \) can be confirmed by different tests like observing the gas turning lime water milky due to the formation of calcium carbonate. The understanding of how carbon dioxide is formed through chemical reactions helps in various scientific and industrial applications.

Thermal Decomposition

Thermal decomposition is a type of chemical reaction where a compound is broken down into simpler substances when heated. This process is crucial in understanding how different compounds react to heat and is widely used across various scientific fields.In the case of sodium carbonate, thermal decomposition results in the breakdown of the compound into sodium oxide \( \mathrm{Na}_2\mathrm{O} \) and carbon dioxide \( \mathrm{CO}_2 \). This reaction can be represented by the equation: \[ \mathrm{Na}_2\mathrm{CO}_3 (s) \rightarrow \mathrm{Na}_2\mathrm{O} (s) + \mathrm{CO}_2 (g) \]The ability to predict and analyze such reactions is significant in industrial processes, environmental science, and chemistry-related fields.

Chemical Reactions

Chemical reactions describe the transformation of reactants into products through breaking and forming chemical bonds. They can be categorized based on different criteria like temperature, products formed, or whether they release or absorb energy. The thermal decomposition of sodium carbonate is a clear example of a chemical reaction, specifically a decomposition reaction. Here, a single compound breaks down into two or more simpler products. Understanding chemical reactions is fundamental to chemistry, providing insights into how different substances interact. Reactions like these are not only important in academic settings but also vital in numerous industries, where they determine the feasibility and cost-effectiveness of various manufacturing processes.