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

Question

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

Step-by-Step Solution

Answer

The reaction produces chlorine (c).

Step 1: Identify Reactants

In the given reaction, bleaching powder, which is chemically known as calcium hypochlorite, reacts with concentrated hydrochloric acid (HCl). The chemical formula for bleaching powder is \(\text{Ca(OCl)}_2\).

Step 2: Write the Chemical Equation

The reaction can be described by the equation: \[ \text{Ca(OCl)}_2 + 2\text{HCl} \rightarrow 2\text{Cl}_2 + \text{CaCl}_2 + 2\text{H}_2\text{O} \] Here, \(\text{Cl}_2\) (chlorine gas) is released.

Step 3: Analyze the Reaction Outcome

Upon inspecting the products of the reaction, it's clear that chlorine gas (\(\text{Cl}_2\)) is produced. This indicates the correct answer among the given options.

Key Concepts

Calcium Hypochlorite

Calcium hypochlorite is a chemical compound with the formula \(\text{Ca(OCl)}_2\). It's commonly known as bleaching powder due to its potent properties in disinfecting and bleaching. This compound is widely used in cleaning and water treatment processes. Calcium hypochlorite is composed of:

• Calcium, a soft gray metal that is an alkaline earth metal.
• Hypochlorite ions, which are the active bleaching agents.

When in water, calcium hypochlorite produces hypochlorous acid, which is responsible for its disinfecting abilities. It's important to note that calcium hypochlorite should be handled with care as it can react with other chemicals, releasing gases like chlorine. This is why understanding its behavior in reactions is crucial.

Chemical Equation

Chemical equations are fundamental for describing chemical reactions. They provide a way to visualize what happens during a reaction. In the case of calcium hypochlorite reacting with hydrochloric acid, the chemical equation is:\[ \text{Ca(OCl)}_2 + 2\text{HCl} \rightarrow 2\text{Cl}_2 + \text{CaCl}_2 + 2\text{H}_2\text{O} \] This equation shows us:

• The reactants: Calcium hypochlorite \(\text{Ca(OCl)}_2\) and hydrochloric acid \(\text{HCl}\).
• The products: Chlorine gas \(\text{Cl}_2\), calcium chloride \(\text{CaCl}_2\), and water \(\text{H}_2\text{O}\).

A balanced chemical equation like this one ensures the same number of each type of atom on both sides. It reflects the conservation of mass, a principle that states that mass is neither created nor destroyed in a chemical reaction. Understanding how to balance and interpret chemical equations is essential for mastering chemistry.

Chlorine Gas Production

In the reaction of calcium hypochlorite with hydrochloric acid, chlorine gas is one of the products formed. Chlorine gas has a chemical formula of \(\text{Cl}_2\), and it's known for its greenish-yellow color and strong, pungent smell. The production of chlorine gas is crucial in various industrial and cleaning processes:

• It is used as a disinfectant in swimming pools due to its ability to kill bacteria and other microbes.
• In the chemical industry, it serves as a key ingredient in the production of many products.
• It’s also utilized in water treatment to make water safe to drink.

However, one must be careful, as chlorine gas is toxic when inhaled and can cause irritation to the eyes and respiratory system. This reaction reminded us how important it is to handle chemicals safely and understand the implications of the gases and substances released in chemical processes.