Problem 54 - A Complete Resource Book in Chemistry for JEE Main

Question

The reaction of slaked lime with \(\mathrm{Cl}_{2}\) gas gives (a) a mixture of \(\mathrm{Ca}(\mathrm{OCl})_{2}, \mathrm{Ca}(\mathrm{OH})_{2}, \mathrm{CaCl}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) (b) quick lime (c) Baryta water (d) only \(\mathrm{Ca}(\mathrm{OCl})_{2}\)

Step-by-Step Solution

Answer

(a) a mixture of \( \text{Ca(OCl)}_2, \text{Ca(OH)}_2, \text{CaCl}_2 \) and \( \text{H}_2\text{O} \).

Step 1: Identifying the Reactants

The reactants in the reaction are slaked lime, which is chemically represented as \( \text{Ca(OH)}_2 \), and chlorine gas \( \text{Cl}_2 \).

Step 2: Writing the Chemical Equation

The chemical reaction for slaked lime reacting with chlorine gas is: \[ \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)}_2 + \text{CaCl}_2 + \text{H}_2\text{O} \]This equation shows that the products formed include calcium hypochlorite \( \text{Ca(OCl)}_2 \), calcium chloride \( \text{CaCl}_2 \), and water \( \text{H}_2\text{O} \).

Step 3: Analyzing the Products

The products from the equation include a mixture of \( \text{Ca(OCl)}_2 \), \( \text{CaCl}_2 \), and \( \text{H}_2\text{O} \). Since slaked lime is also present as \( \text{Ca(OH)}_2 \), the mixture indeed contains these four compounds: \( \text{Ca(OCl)}_2 \), \( \text{Ca(OH)}_2 \), \( \text{CaCl}_2 \), and \( \text{H}_2O \).

Step 4: Selecting the Correct Option

Comparing the analysis of products with the given options, the correct answer is option (a), which states that the reaction produces a mixture of \( \text{Ca(OCl)}_2 \), \( \text{Ca(OH)}_2 \), \( \text{CaCl}_2 \), and \( \text{H}_2\text{O} \).

Key Concepts

Calcium Hypochlorite Formation

Calcium hypochlorite, represented by the chemical formula \( \text{Ca(OCl)}_2 \), is an important compound formed when slaked lime reacts with chlorine gas. Slaked lime, which is scientifically known as calcium hydroxide \( \text{Ca(OH)}_2 \), reacts with chlorine \( \text{Cl}_2 \) to produce this bleaching agent.
Calcium hypochlorite is widely used in disinfecting water in swimming pools. The chemical reaction is a slow but continuous process that effectively sanitizes large volumes of water.
In the reaction, you have:

• Calcium hypochlorite \( \text{Ca(OCl)}_2 \) as a key product used for disinfection
• Formation occurs alongside other compounds such as calcium chloride \( \text{CaCl}_2 \), which is a by-product in this scenario

Understanding this reaction helps comprehend how multiple products can emerge from a single chemical interaction.

Chemical Reaction Analysis

Analyzing the chemical reaction involves breaking down the components, examining the reactants and products, and understanding how they transform during the process. In this scenario, you start with slaked lime and chlorine gas as the reactants.
The balanced chemical equation for the reaction is: \[ \text{Ca(OH)}_2 + \text{Cl}_2 \rightarrow \text{Ca(OCl)}_2 + \text{CaCl}_2 + \text{H}_2\text{O} \] Let's go through it step by step:

• The reactant \( \text{Ca(OH)}_2 \) reacts with chlorine gas \( \text{Cl}_2 \)
• They produce calcium hypochlorite \( \text{Ca(OCl)}_2 \), calcium chloride \( \text{CaCl}_2 \), and water \( \text{H}_2\text{O} \)

The reaction involves a substitution mechanism where chlorine displaces the hydroxide ions and contributes to the formation of hypochlorite and chloride ions. This process showcases how reactions can lead to the creation of new substances under the right conditions.

Products of Chemical Reactions

Products of chemical reactions vary widely based on the reactants involved and the conditions under which the reaction takes place. When slaked lime reacts with chlorine gas, the products formed include a mix of different chemicals.
The main products are:

• Calcium hypochlorite \( \text{Ca(OCl)}_2 \)
• Calcium chloride \( \text{CaCl}_2 \)
• Water \( \text{H}_2\text{O} \)

Slaked lime, \( \text{Ca(OH)}_2 \), is also present in the mixture if not fully reacted.
This combination signifies that reactions can create a mixture of substances rather than a singular product. The presence of each compound is due to the specific pathway that the chemical reaction follows. Recognizing these outcome products helps in determining their practical applications and implications in various fields such as water treatment and chemical manufacturing.