Problem 5 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is formed when sodium sulphate is boiled with powered sulphur? (a) \(\mathrm{NaHSO}_{4}\) (b) \(\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}\) (c) \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) (d) \(\mathrm{Na}_{2} \mathrm{~S}_{4} \mathrm{O}_{6}\)

Step-by-Step Solution

Answer

The product formed is \(\mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3\) (option b).

Step 1: Understanding the Reaction

We begin by analyzing the reaction in question. Sodium sulphate (\(\mathrm{Na}_2\mathrm{SO}_4\)) is boiled with powdered sulfur (\(\mathrm{S}\)). We want to identify the product formed from this reaction.

Step 2: Reaction Prediction

Sodium thiosulphate (\(\mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3\)) is commonly formed when sodium sulphate reacts with sulfur. The reaction is: \[\mathrm{Na}_2\mathrm{SO}_4 + \mathrm{2S} \rightarrow \mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3\] This indicates that option (b) \(\mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3\) is likely the correct product.

Step 3: Verification of the Product

Let's confirm. The reaction between \(\mathrm{Na}_2\mathrm{SO}_4\) and \(\mathrm{S}\) to form \(\mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3\) is a known redox transformation that occurs due to the sulfur's ability to oxidize/change state, which supports the formation of thiosulphate.

Key Concepts

Sodium Sulphate

Sodium sulphate, , is a well-known inorganic compound widely used in various industrial applications. It is a white, crystalline solid that is highly soluble in water. It can be found in its naturally occurring form, known as mirabilite, or synthesized industrially from natural resources. In laboratories and industrial settings, the distinct properties of sodium sulfate make it a suitable reactant for chemical processes and synthesis.
One of the key characteristics of sodium sulphate is its stability at room temperature, enabling its widespread use. When introduced to heat or boiled, it can participate in numerous reactions, such as the reaction with sulfur, as seen in the exercise context. Understanding the compound's tendencies, like its ability to produce salts when reacting with other substances, is crucial for comprehending its role in chemical processes and experiments.

Thiosulfate Formation

The formation of thiosulfate is a fascinating reaction, particularly when considering its synthesis from sodium sulphate and sulfur. Sodium thiosulfate, , is produced through a chemical transformation in which elemental sulfur is added to sodium sulphate. The reaction is as follows: This formation is considered a redox transformation where sulfur acts as both the oxidizing and reducing agent. The resultant thiosulfate anion, ,- is characterized by its two sulfur atoms connected by a sulfur-sulfur bond, reflecting its distinct structure from sulfate.
The importance of thiosulfate extends beyond its chemical formation. It is frequently utilized in industries as a fixing agent for photography, a reducing agent in gold extraction, or an additive in chemicals and pharmaceuticals. Comprehending how thiosulfate is formed and its broader applications provides insight into the dynamic role it plays in both chemical reactions and industrial processes.

Redox Reactions

Redox reactions are a fundamental concept in chemistry that involve the transfer of electrons between two species. In the reaction of sodium sulphate and sulfur leading to the formation of sodium thiosulfate, a redox reaction is indeed taking place. Specifically, sulfur undergoes a change in oxidation state, which is central to this process.
In this reaction, sulfur acts as both the oxidizing and reducing agent. It accepts electrons, thus being reduced, and donates electrons, thus being oxidized in the process of transforming sodium sulphate into sodium thiosulfate. This dual role is characteristic of redox reactions and underlines their complex yet essential nature in chemistry.
Understanding redox reactions is crucial for students as it not only applies to laboratory chemistry but also to numerous real-world chemical processes. These include the rusting of iron, biological processes in the human body, and the functioning of batteries. Learning about redox chemistry equips students with a greater comprehension of how substances interact at a molecular level, predicting the behavior of different reactants in a variety of conditions.