Problem 13 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following does not precipitate in the Solvay process, for the manufacture of \(\mathrm{Na}_{2} \mathrm{CO}_{3}{\underline{\phantom{xx}}}^{2}\) ? (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (c) \(\mathrm{NH}_{3}\) (d) \(\mathrm{NaCl}\) solution

Step-by-Step Solution

Answer

(b) H₂SO₄ does not precipitate in the Solvay process, as it is not used.

Step 1: Understand the Solvay Process

The Solvay process is a method to manufacture sodium carbonate (Na₂CO₃). It involves the reaction of sodium chloride (NaCl), ammonia (NH₃), and carbon dioxide (CO₂) in water. The key precipitant formed in this process is sodium bicarbonate (NaHCO₃) which can be further heated to give sodium carbonate.

Step 2: Identify the Compounds in the Solvay Process

The main compounds involved in the Solvay process include CO₂, NH₃, and NaCl. These react together, in the presence of water, to produce the desired products. None of these compounds directly precipitates out as solids; instead, they contribute to the formation of precipitated intermediates such as NaHCO₃.

Step 3: Determine the Role of H₂SO₄

H₂SO₄, or sulfuric acid, is not typically involved in the Solvay process. The process mainly relies on the chemical reactions between NaCl, NH₃, and CO₂. Because H₂SO₄ does not participate in the main reactions or precipitate formation, it is the odd one out in this list.

Step 4: Recognize Precipitation in the Process

In the Solvay process, NaHCO₃ is the compound that actually precipitates out as a solid. None of the other listed compounds (CO₂, NH₃, or NaCl) do so. H₂SO₄ does not even react or get used at all.

Step 5: Conclusion

Based on the Solvay process, only NaHCO₃, not any of the listed options, is a precipitated product. Since H₂SO₄ isn't involved or used, it cannot precipitate in this process.

Key Concepts

Sodium Carbonate

Sodium carbonate, also known as soda ash or washing soda, is a highly useful chemical compound with the formula \( \text{Na}_2\text{CO}_3 \). It appears as a white, crystalline powder and is soluble in water. When dissolved, it creates an alkaline solution.
One of the main methods of producing sodium carbonate is through the Solvay process, an industrial process that creates soda ash using relatively common and inexpensive raw materials. Sodium carbonate is involved in numerous applications.

**Applications of Sodium Carbonate**

• Laundry and cleaning agents: Sodium carbonate is used as a water softener in washing powders.
• Glass manufacturing: It reduces the melting point of quartz, facilitating glass production.
• Food industry: Acts as a food additive in some cases.
• Chemicals: Used in the production of other sodium compounds, like sodium bicarbonate.

The chemical properties of \( \text{Na}_2\text{CO}_3 \) make it an essential substance in various industries, proving its versatility and importance.

Precipitation Reactions

Precipitation reactions are chemical reactions that result in the formation of an insoluble solid, known as the precipitate, from two or more solutions.
In the case of the Solvay process, the primary precipitation reaction involves the formation of sodium bicarbonate \( \text{NaHCO}_3 \). This occurs when a solution of ammonium bicarbonate \( \text{NH}_4\text{HCO}_3 \) reacts with a saturated solution of sodium chloride \( \text{NaCl} \).

The reaction is as follows:
\[ \text{NH}_4\text{HCO}_3 (aq) + \text{NaCl} (aq) \rightarrow \text{NaHCO}_3 (s) + \text{NH}_4\text{Cl} (aq) \]

**Characteristics of Precipitation Reactions**

• Occurs when certain ions in a solution form an insoluble compound.
• Common in the preparation of various industrial products.
• The precipitated product is collected by filtration, centrifugation, or sedimentation.

Understanding precipitation reactions is crucial, as they play a vital role in the Solvay process and many other chemical manufacturing techniques.

Chemistry

Chemistry is the scientific study of the properties and behavior of matter. It encompasses a wide range of topics from atomic interactions to the building blocks of many materials we use.
In the context of the Solvay process, chemistry sets the stage for understanding how different compounds react with one another to form new products. The Solvay process wonderfully illustrates several key chemical concepts:

**Important Chemistry Concepts**

• Reactivity: How different chemicals, like CO₂, NH₃, and NaCl, react to form new compounds.
• Solubility: The ability of compounds to dissolve in solvents, affecting precipitation.
• Equilibrium: Many reactions in the Solvay process reach a state of equilibrium where reactants and products are balanced.

By understanding chemistry, one can appreciate how simple substances transform into valuable compounds like sodium carbonate. Each reaction step, balance of materials, and resulting end product highlights the intricate dance of elements and compounds.