Problem 80 - A Complete Resource Book in Chemistry for JEE Main

Question

Bleaching powder reacts with a few drops of concentrated HCl to give (a) oxygen (b) calcium oxide (c) chlorine (d) hypochlorous acid

Step-by-Step Solution

Answer

(c) chlorine

Step 1: Understand the Chemical Reaction

Bleaching powder, known chemically as calcium hypochlorite ( ext{Ca(OCl)_2}), reacts with concentrated hydrochloric acid ( ext{HCl}). The chemical reaction typically involves the products being calcium chloride ( ext{CaCl_2}), water ( ext{H_2O}), and chlorine gas ( ext{Cl_2}).

Step 2: Write the Chemical Equation

The balanced chemical equation for the reaction between bleaching powder (calcium hypochlorite) and hydrochloric acid is: \[ \text{Ca(OCl)_2} + 4\text{HCl} \rightarrow \text{CaCl}_2 + 2\text{H_2O} + 2\text{Cl}_2 \] This shows that chlorine gas is produced as one of the products.

Step 3: Identify the Product Asked

The problem asks which product is formed. In the reaction, chlorine gas ( ext{Cl}_2) is one of the products. It is generated as a result of the reaction between bleaching powder and concentrated hydrochloric acid.

Key Concepts

Calcium Hypochlorite

Calcium hypochlorite is a chemical compound with the formula \(\text{Ca(OCl)}_2\). It is commonly known as bleaching powder and is widely used for its powerful disinfecting properties. Typically, it serves as an effective bleaching agent and can purify water. This compound appears as a white powder with a strong odor resembling chlorine. Its disinfectant capability makes it prevalent in sanitizing swimming pools and treating drinking water to eliminate harmful microorganisms.

When calcium hypochlorite reacts chemically with substances, it often acts as an oxidizing agent. An oxidizing agent is a substance that can accept electrons from another substance during a reaction.

• Calcium hypochlorite releases chlorine gas upon reaction with certain acids, including hydrochloric acid.
• The compound's effectiveness in bleaching and disinfecting is due to its ability to release reactive chlorine.

Hydrochloric Acid

Hydrochloric acid (HCl) is a strong, corrosive acid often utilized in various chemical processes. It is a solution of hydrogen chloride gas in water. In its pure state, it is a clear, colorless liquid with a distinctive, pungent smell.

In industrial and laboratory settings, hydrochloric acid is employed for its ability to react quickly with various substances, such as metals and bases. It completely dissociates in water to produce hydronium (\(\text{H}_3\text{O}^+\)) and chloride ions (\(\text{Cl}^-\)). This characteristic accounts for its potent corrosive properties.

• Hydrochloric acid has significant applications, including in the production of organic compounds and in refining metal.
• It reacts with calcium hypochlorite to release chlorine gas, a crucial point discussed in chemical reaction exercises.

Chlorine Gas Production

Chlorine gas (\(\text{Cl}_2\)) is a greenish-yellow gaseous compound. It is critical in numerous chemical processes and industrial applications. Known for its distinct, sharp smell, chlorine gas can be harmful if inhaled, requiring careful handling.

During chemical reactions, such as between calcium hypochlorite and hydrochloric acid, chlorine gas becomes one of the by-products. Understanding the conditions under which chlorine is produced helps in controlling the processes in industries effectively.

• Chlorine gas is often used for producing disinfectants and in water purification.
• Its production through controlled reactions helps in generating chlorine in desired amounts for specific applications like water treatment.

In the discussion above, we can observe that the chemical reaction not only serves scientific curiosity but also direct applications in real-world scenarios, illustrating the utility of chemical reactions in everyday life.