Problem 81 - A Complete Resource Book in Chemistry for JEE Main

Question

When chlorine is passed over dry slaked lime at room temperature, the main reaction product is (a) \(\mathrm{CaCl}_{2}\) (b) \(\mathrm{Ca}(\mathrm{OCl})_{2}\) (c) \(\mathrm{Ca}\left(\mathrm{ClO}_{2}\right)_{2}\) (d) \(\mathrm{CaOCl}_{2}\)

Step-by-Step Solution

Answer

The main reaction product is (d) \(\mathrm{CaOCl}_2\).

Step 1: Identify Reactants

The problem states that chlorine gas ( ext{Cl}_2 ext{)) is passed over dry slaked lime ( ext{Ca(OH)}_2 ext{)). These are the reactants in the chemical reaction whose product we need to identify.

Step 2: Write the Chemical Equation

The common reaction when chlorine interacts with slaked lime is the formation of bleaching powder. The chemical equation for this reaction is: \[ \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)}_2 + \text{CaCl}_2 + 2\text{H}_2\text{O} \]However, under typical conditions, the main product sought in such queries is \( \text{Ca(OCl)Cl} \).

Step 3: Simplify to Main Reaction Product

In industry and academic problems, the formation of bleaching powder is often simplified to its main component. Thus, when considering the simplified main product, the reaction is written as: \[ \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)Cl} + \text{H}_2\text{O} \]Here, \( \text{Ca(OCl)Cl} \) is calcium oxychloride or bleaching powder.

Step 4: Select the Correct Option

Based on the simplified reaction, the main reaction product is calcium oxychloride, which is represented by \( \text{Ca(OCl)Cl} \). The equivalent option in the given choices for this product is (d) \( \text{CaOCl}_2 \).

Key Concepts

Chlorine and slaked lime reaction

When chlorine gas interacts with slaked lime, a fascinating chemical reaction occurs. This experiment is not just academically interesting; it's also industrially significant. Slaked lime, which is chemically known as calcium hydroxide \( \text{Ca(OH)}_2 \), is a common and useful substance.

• Chlorine, represented by \( \text{Cl}_2 \), is a diatomic molecule, noted for its pungent odor and greenish-yellow color.
• When passed over slaked lime at room temperature, these two substances interact, kicking off a chemical reaction.

The basic chemical equation for their reaction can be simplified to: \[ \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)Cl} + \text{H}_2\text{O} \] This equation shows how slaked lime and chlorine result in the formation of calcium oxychloride (also known as bleaching powder) and water. Understanding this reaction deepens comprehension of both industrial processes and basic chemistry concepts.

Bleaching powder production

The production of bleaching powder is a key outcome of the interaction between chlorine and slaked lime. Bleaching powder, known chemically as calcium oxychloride, has a variety of applications. It plays an important role in several industries due to its disinfectant properties.

• Its preparation occurs through the passage of chlorine gas over dry slaked lime - a straightforward yet significant process.
• This produces a compound used worldwide for water treatment, bleaching in the textile industry, and as a sanitizing agent.

What differentiates bleaching powder in this reaction is the intentional creation of a stable compound. The simplified reaction: \[ \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)Cl} + \text{H}_2\text{O} \] Illustrates how two simple reactants create a versatile product. The powder's chemical structure ensures it can slowly release chlorine, making it effective as a bleaching and disinfecting agent.

Calcium oxychloride

Calcium oxychloride is the main product of the reaction between chlorine and slaked lime. With chemical formula \( \text{Ca(OCl)Cl} \), it is more commonly referred to as bleaching powder.

• This compound showcases a balance of chlorine, oxygen, and calcium, granting it unique properties useful in multiple fields.
• Its ability to release chlorine steadily makes it effective for purifying water or sanitizing surfaces.

Moreover, calcium oxychloride is also handled carefully to prevent moisture exposure, as it can react further with water. This quality adds robustness to its use as a bleaching and disinfectant agent, perpetuating its demand across various industries.Understanding the chemistry and uses of calcium oxychloride underscores its importance, not just as a standalone chemical, but as a vital component of public health initiatives, ensuring clean water and hygienic environments.