Problem 106 - A Complete Resource Book in Chemistry for JEE Main

Question

Which is correct statement here? (1) Glacial acetic acid is used as a solvent in the preparation of p-nitroacetanilide. (2) Potash alum is used as a mordant in dyeing. (3) Potassium alum is used to remove positively charged impurities from water. (4) Iodoform has antiseptic properties also. (a) 2 and 4 (b) 1,3 and 4 (c) 1 and 3 (d) 1,2 and 4

Step-by-Step Solution

Answer

Option (d): 1, 2, and 4 are correct statements.

Step 1: Understanding Glacial Acetic Acid

Glacial acetic acid is a concentrated form of acetic acid and is often used as a solvent in organic synthesis. It is known to be used as a solvent in the preparation of p-nitroacetanilide, making statement 1 true.

Step 2: Examining Potash Alum as a Mordant

Potash alum (potassium aluminum sulfate) serves as a mordant in the dyeing process. A mordant is a substance used to set dyes on fabrics or tissues, which confirms statement 2 as true.

Step 3: Evaluating Potassium Alum’s Role in Water Purification

Potassium alum is actually used to remove negatively charged impurities from water, not positively charged ones as mentioned in statement 3. Therefore, statement 3 is false.

Step 4: Considering Antiseptic Properties of Iodoform

Iodoform (CHI3) is known to have antiseptic properties, which makes statement 4 true.

Step 5: Analyzing Provided Options

Now that we have determined which statements are true, we compare them with the options provided: - Option (a): 2 and 4 - Option (b): 1, 3 and 4 - Option (c): 1 and 3 - Option (d): 1, 2 and 4 Only option (d) with statements 1, 2, and 4 being correct aligns with our findings.

Key Concepts

Glacial Acetic Acid

Glacial acetic acid is the concentrated form of acetic acid, and is so-called because it can form ice-like crystals in cold temperatures. With a purity level hovering around 99%, it's highly corrosive and should be handled with care. This compound plays a crucial role in organic synthesis due to its use as a solvent, particularly for reactions where water may interfere. A common application includes the preparation of p-nitroacetanilide. Here, glacial acetic acid assists in facilitating the reaction by ensuring that the reactants interact as intended, thus proving to be a vital component in the synthesis process.

Potash Alum in Dyeing

Potash alum, known chemically as potassium aluminum sulfate, acts as a mordant in the dyeing industry. A mordant is an agent that helps dyes bind to fibers, ensuring that the color is both vibrant and durable. By forming a complex with the dye and fiber, potash alum enhances color fastness and prevents the dye from washing out easily.
In practice, fibers or fabrics are often soaked in a mordant solution before or during the dyeing process. This step is crucial as it improves the bonding between the dye molecules and the fibers, resulting in a richer and more permanent color.
Its role as a bridging agent in dyeing highlights its importance in textile applications.

Iodoform Antiseptic Properties

Iodoform, with its chemical formula CHI₃, is a compound known for its antiseptic properties. The characteristic yellow, crystalline form of iodoform is often used in medical settings for its ability to disinfect. It properties are due to its ability to release iodine slowly, which helps in killing bacteria and cleansing wounds.
Historically, iodoform was applied directly to wounds or used as an antiseptic dressing, making it a staple for preventing infections. Although less common today due to the development of more efficient antiseptics, iodoform still holds a place in practices respecting traditional treatment methods.

Water Purification Chemicals

In water purification, various chemicals are used to ensure that impurities are removed effectively. Potassium alum is one such chemical, commonly used to remove negatively charged impurities from water. This process is essential for making water safe to consume and use.
Potassium alum works by causing the suspended particles in the water to clump together, forming larger particles that can be easily filtered out. This process, known as coagulation, is a vital step in water treatment installations. By attracting and binding particles, potassium alum helps to clear the water and reduce turbidity, resulting in cleaner and safer water for various uses.