Problem 71 - A Complete Resource Book in Chemistry for JEE Main

Question

What are the products formed when chlorine is passed through aqueous hypo solution? (a) \(\mathrm{Na}_{2} \mathrm{SO}_{3}+\mathrm{SO}_{3}+\mathrm{HCl}\) (b) \(\mathrm{Na}_{2} \mathrm{SO}_{3}+\mathrm{HCl}+\mathrm{S}\) (c) \(\mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{HCl}+\mathrm{SO}_{2}\) (d) \(\mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{HCl}+\mathrm{S}\)

Step-by-Step Solution

Answer

The correct products are in option (d): \( \mathrm{Na}_2 \mathrm{SO}_4+\mathrm{HCl}+\mathrm{S} \).

Step 1: Identify the Reactants

The question asks for the products formed when chlorine gas (Cl₂) is passed through aqueous solution of sodium thiosulfate (Na₂S₂O₃), commonly referred to as hypo.

Step 2: Write the Balanced Chemical Equation

The chemical reaction for this process is:\[ \mathrm{Na}_2\mathrm{S}_2\mathrm{O}_3 + \mathrm{Cl}_2 + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{Na}_2\mathrm{SO}_4 + \mathrm{HCl} + \mathrm{S} \]

Step 3: Analyze the Products

From the balanced equation, the products formed in the reaction are sodium sulfate (Na₂SO₄), hydrochloric acid (HCl), and elemental sulfur (S).

Step 4: Match with Given Options

Compare the products obtained with the options provided in the question. The correct option that matches the products is (d) \( \mathrm{Na}_2 \mathrm{SO}_4+\mathrm{HCl}+\mathrm{S} \).

Key Concepts

Chlorine

Chlorine is a highly reactive element found in the halogen group of the periodic table, represented by the symbol \( \text{Cl} \). It exists as a greenish-yellow gas at room temperature and is known for its strong odor.
Chlorine is widely used in various industrial and household applications:

• In water treatment, it acts as a disinfectant due to its antimicrobial properties.
• As a bleaching agent, it is used in the paper and textile industries.
• It serves as a crucial component in the manufacturing of pharmaceuticals and other chemicals.

Its high reactivity allows it to partake in numerous chemical reactions, such as the reaction with aqueous sodium thiosulfate, where it acts first as an oxidizing agent. The knowledge of chlorine's behavior is vital in mastering its applications in both basic and complex chemical processes.

Aqueous Solutions

An aqueous solution is a solution in which water acts as the solvent. When a solid, liquid, or gas dissolves in water, it turns into an aqueous state represented by the symbol \( \text{(aq)} \).
In this reaction, sodium thiosulfate is dissolved in water to form an aqueous solution, making it available for chemical reactions with gases like chlorine. This kind of solution allows ions and molecules to interact freely:

• Water, being a polar solvent, can dissolve many ionic compounds and polar molecules efficiently.
• Aqueous solutions play a pivotal role in biological systems and various chemical reactions.
• They allow substances to be transported easily, particularly in biological systems, as blood plasma is mostly water.

Aqueous solutions are essential in laboratory settings for conducting reactions akin to the reaction of sodium thiosulfate and chlorine, permitting reactants to collide with sufficient energy to break bonds and form products.

Sodium Thiosulfate

Sodium thiosulfate, chemically represented as \( \text{Na}_2\text{S}_2\text{O}_3 \), is a crystalline compound commonly referred to as 'hypo'. It serves many purposes and is well-known for:

• Its application as a photographic fixer in traditional development processes.
• Being used in iodine clock reactions, a popular demonstration in chemistry classrooms.
• Its utilization in dechlorination of tap water in aquariums.

In the reaction with chlorine, sodium thiosulfate acts as a reducing agent, donating electrons to chlorine, allowing for the conversion of sodium thiosulfate to sodium sulfate, and releasing sulfur along with hydrochloric acid. This showcases its ability to undergo transformation by interacting with oxidizing agents.

Balanced Chemical Equations

Balanced chemical equations are a fundamental part of understanding chemical reactions. They depict the reactants and products involved, ensuring the conservation of both mass and charge:

• By writing a balanced equation, you verify that the number of each type of atom on the reactant side equals the number on the product side.
• The coefficients in front of compounds and elements represent the number of moles, allowing you to predict the quantities involved in the reaction.
• Balancing equations is essential for determining the stoichiometry of a reaction, which is vital for practical applications, like chemical synthesis.

For example, the equation \( \text{Na}_2\text{S}_2\text{O}_3 + \text{Cl}_2 + \text{H}_2\text{O} \rightarrow \text{Na}_2\text{SO}_4 + \text{HCl} + \text{S} \) is balanced because the same number of each element's atoms are present on both sides. Balancing chemical equations helps students and professionals alike in predicting how different chemicals will react and in what proportions.