NEET Chemistry: Dyes and Pigments questions with solutions

Q1. Reactive dyes utilize a attached to a substituent that is capable of directly reacting with the fibre substrate.

1. chromophore
2. auxochrome
3. chlorophyll
4. none of the above

Answer: chromophore

The chromophore is the color-producing part of a dye molecule, and in reactive dyes it is attached to a substituent that can react with the fiber. This design lets the dye form a covalent bond with the substrate.

Q2. What is the name for red azo dye?

1. p-hydroxy azo benzene
2. \( \beta \) - nathyl azo benzene
3. p-amino azo benzene
4. p- \( \mathrm{N}, \mathrm{N} \) dimethyl amino azo benzene

Answer: p- \( \mathrm{N}, \mathrm{N} \) dimethyl amino azo benzene

p-N,N-dimethylamino azo benzene is the red azo dye because the dimethylamino group extends conjugation and shifts absorption into the visible red region. The other options correspond to different azo compounds with different colors or properties.