Problem 6 - Chemistry in 30 days

Question

Bleaching powder is prepared by passing chlorine into (a) \(\mathrm{Ca}(\mathrm{OCl})_{2}\) (b) \(\mathrm{Ca}(\mathrm{OH})_{2}\) (c) \(\overline{\mathrm{CaH}}\). (d) \(\mathrm{Ca}(\mathrm{ClO}\)

Step-by-Step Solution

Answer

Bleaching powder is prepared by passing chlorine into \(\mathrm{Ca(OH)}_2\).

Step 1: Understanding the Chemical Process

To solve this question, we need to understand how bleaching powder is prepared. Bleaching powder is chemically known as calcium hypochlorite, and it is typically produced by the reaction of chlorine gas with calcium hydroxide.

Step 2: Identifying the Correct Reactant

The compound that reacts with chlorine to form bleaching powder is calcium hydroxide, which has the chemical formula \(\mathrm{Ca(OH)}_2\).

Step 3: Verifying the Chemical Formula

We verify our understanding by writing out the chemical equation for the preparation of bleaching powder: \(\mathrm{2Cl}_2 + 2\mathrm{Ca(OH)}_2 \rightarrow \mathrm{Ca(OCl)}_2 + \mathrm{CaCl}_2 + 2\mathrm{H}_2\mathrm{O}\). This confirms that chlorine reacts with \(\mathrm{Ca(OH)}_2\) to form bleaching powder.

Key Concepts

Chlorine Gas Reaction

The reaction of chlorine gas is a fundamental process in the production of bleaching powder. When chlorine gas ( \(\text{Cl}_2\)) is introduced, it acts as a powerful oxidizing agent, meaning it has the ability to accept electrons from other substances during a chemical reaction. This property is what enables chlorine to react effectively with compounds such as calcium hydroxide. In the specific process of creating bleaching powder, chlorine gas is bubbled through a solution containing calcium hydroxide. The interaction leads to the production of several byproducts, including calcium hypochlorite, which is the main active ingredient in bleaching powder.**Important Aspects to Note:**

• Chlorine gas is highly reactive and needs to be handled with care due to its toxic nature.
• The reaction requires excess chlorine gas to ensure maximum yield of the products.
• This process typically occurs in a controlled environment to manage the gas emissions efficiently.

Calcium Hydroxide

Calcium hydroxide, also known as slaked lime, is a critical reactant in the preparation of bleaching powder. Its chemical formula is \(\text{Ca(OH)}_2\). As a white powder or crystal, it is slightly soluble in water, forming a solution that is alkaline in nature.When calcium hydroxide reacts with chlorine, it results in the formation of two primary compounds: calcium hypochlorite and calcium chloride. The chemical equation representing this process is:\[ \text{2Cl}_2 + 2\text{Ca(OH)}_2 \rightarrow \text{Ca(OCl)}_2 + \text{CaCl}_2 + 2\text{H}_2\text{O} \]This illustrates how two molecules of chlorine gas react with two molecules of calcium hydroxide to eventually form calcium hypochlorite - the active component of bleaching powder.**Key Characteristics of Calcium Hydroxide:**

• It is a source of calcium ions, which are necessary for the reaction.
• The presence of hydroxide ions means it can neutralize acids and acidic gases.
• It is used not only in bleaching but also in water treatment and as a pH regulator.

Calcium Hypochlorite

Calcium hypochlorite, denoted as \(\text{Ca(OCl)}_2\), is the primary product of the reaction between chlorine gas and calcium hydroxide. It serves as the active ingredient in bleaching powder, which is widely utilized for its disinfectant and bleaching properties.The presence of hypochlorite ions (\(\text{OCl}^-\)) in calcium hypochlorite gives it strong oxidizing abilities, making it effective in killing bacteria and other microorganisms. This makes calcium hypochlorite an essential component in household bleach as well as in water sanitation practices.**Notable Uses and Properties:**

• It acts as a chlorine-releasing agent, which is crucial for sanitation and bleaching.
• Aside from bleaching, it is also used extensively for sanitizing swimming pools to keep the water safe and clean.
• Calcium hypochlorite is stable in dry form but should be stored properly as it can react with moisture and other impurities.