MCQ Detailed View

Alum is a chemical compound commonly used in dyeing fabrics. A mordant is a substance that helps the dye attach to the fibers of cloth. Alum acts as a mordant by forming a coordination complex with the dye molecules and the fabric. This process ensures that the colors are more vivid, uniform, and durable. Without a mordant like alum, many dyes would wash out quickly or appear dull.

Chemically, alum is a type of double salt, usually potassium aluminum sulfate. It is soluble in water and can interact with both natural and synthetic dyes. The positive ions in alum help the negatively charged dye molecules bind to the negatively charged fiber surface. This chemical interaction is why alum is preferred in textile dyeing.

Alum also has other minor uses in water purification and cosmetics, but its main role in dyeing is as a mordant. In dyeing, it is added to the dye bath before or along with the dye. The presence of alum improves color fastness, meaning the fabric maintains its color even after washing or exposure to sunlight.

Other options listed are incorrect for this context. Alum is not used primarily for fireproofing fabrics, softening water, or as a general water purifier in dyeing applications. Its main function is chemical fixation of dyes to textile fibers.

Understanding the role of alum as a mordant helps students learn about practical applications of chemistry in everyday life. It also explains why certain chemicals are chosen to improve the appearance and durability of dyed fabrics in the textile industry.