Question

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

Short answer

H₂SO₄ does not precipitate in the Solvay process.

Step-by-step solution

Understand the Solvay Process

The Solvay process is an industrial method for producing sodium carbonate (Na₂CO₃). It primarily involves the reaction of sodium chloride (NaCl), ammonia (NH₃), and carbon dioxide (CO₂) in water to form sodium bicarbonate (NaHCO₃) and ammonium chloride (NH₄Cl). The sodium bicarbonate is then heated to form sodium carbonate.

Identify Precipitation Reactions

In the Solvay process, CO₂ acts as a reactant. Ammonia (NH₃) is used to react with the dissolved carbon dioxide (CO₂) to form ammonium carbonate, which further reacts to form sodium bicarbonate (NaHCO₃) which precipitates out of the solution. Thus, NaHCO₃ is the substance that precipitates during this process.

Evaluate Each Option

1. CO₂: A reactant in forming NaHCO₃, does not precipitate. 2. H₂SO₄: Not involved in the Solvay process. 3. NH₃: Part of the solution but does not precipitate. 4. NaCl: Soluble in water and provides Na⁺ ions but does not precipitate.

Determine the Element Not Precipitating

H₂SO₄ is not used in the Solvay process, hence it neither reacts nor precipitates. NH₃ and NaCl are part of the solution ingredients but they do not form precipitates themselves while CO₂ is a reactant and remains in solution as it reacts.

Key concepts

Sodium Carbonate Production

Sodium carbonate, commonly known as washing soda, is an essential chemical used in various industries, such as glass manufacturing, detergents, and chemical manufacturing. The primary method of producing sodium carbonate is through the Solvay process. This process begins with the reaction of sodium chloride (NaCl), ammonia (NH₃), and carbon dioxide (CO₂) in the presence of water. The main aim is to convert these inexpensive and widely available raw materials into sodium carbonate (Na₂CO₃).

The Solvay process involves several key chemical reactions and stages. It starts with the dissolution of sodium chloride in water, followed by the introduction of ammonia and carbon dioxide. This combination leads to the formation of sodium bicarbonate (NaHCO₃), which precipitates out of the solution. The sodium bicarbonate is then heated to drive off carbon dioxide and water, leaving behind sodium carbonate. This efficient and cost-effective process is crucial as it minimizes the need for more expensive raw materials and energy-intensive processes found in other methods.

Chemical Reactions in Solvay Process

In the Solvay process, chemical reactions play a crucial role in transforming basic raw materials into sodium carbonate. The sequence of reactions is both fascinating and efficient, allowing the production of sodium carbonate at a large scale.

**Key Reactions in the Solvay Process:**

• Firstly, ammonia is dissolved in water to create ammoniated brine, which serves as a medium for subsequent reactions.
• Then, carbon dioxide is bubbled through this solution. It reacts with the ammonia-water mixture to produce ammonium bicarbonate (NH₄HCO₃).
• The ammonium bicarbonate then reacts with the sodium chloride in the solution, leading to the formation of sodium bicarbonate (NaHCO₃) and ammonium chloride (NH₄Cl).

The newly formed sodium bicarbonate precipitates out of the solution as it is sparingly soluble in cold conditions. The precipitated sodium bicarbonate is then collected and heated, which decomposes it into sodium carbonate and releases carbon dioxide and water. The byproducts, particularly ammonium chloride, can be recycled back into the process, enhancing efficiency and sustainability.

Precipitation Reactions in Chemistry

Precipitation reactions are a fascinating aspect of chemistry where solubility and reactivity come into play. A precipitation reaction occurs when two soluble substances are combined to give an insoluble product, known as a precipitate. This reaction can be utilized to isolate specific compounds, as seen in the Solvay process.

In the context of the Solvay process, sodium bicarbonate is the primary compound that precipitates out as a solid from the solution. When carbon dioxide reacts with the ammoniated brine containing dissolved sodium chloride, sodium bicarbonate is produced. Importantly, sodium bicarbonate is less soluble in the solution, especially at lower temperatures, leading to its precipitation as a solid.

The conditions for a successful precipitation involve considering factors like temperature and the concentrations of the reactants. In general, when designing an industrial process like the Solvay method, gauges are set to ensure maximum yield from these precipitation reactions by adjusting these conditions appropriately. This ensures that precipitation occurs efficiently at each step, allowing for the accumulation of the required product in pure form.