Question

What is a dye?
(A) Dye itself is an element
(B) Dye is a supersaturated solution
(C) Dye is a mixture
(D) Dye is a colloid

Answer 1

Hint: A basic knowledge about dyes is necessary to answer this question. It’s a coloured substance which chemically bonds to the substrate to which it’s being applied. It consists as a mixture of two or more colours.

Complete Solution :
- As we know, dyes are those coloured substances which can mix into a solution in an application process and exhibit colour through the process of selective light absorption. The properties of dyes can be described by their chemical structure.
- They are the chemical compounds which give colour for things like clothes, food, plastic, cosmetics etc., and for artistic colours and inks. Dyes could be classified as synthetic or natural dyes, acid or basic dyes, direct dyes, disperse dyes, pigment dyes, sulfur dyes etc.
- The dyes are intense in colour and they are usually soluble in water. Some of them can be rendered insoluble in addition of salt to produce a lake pigment.
- The process of dyeing involves the transfer of dyes from the aqueous solution onto the fibre surface (adsorption) and dyes getting diffused into the fibre (diffusion).
- Dyes absorb light in the spectrum of visibility which is in the 400-800 nm and they have a conjugated system, at least one chromophore which is a colour-bearing group, and last is that they show electrons resonance, a stabilizing force in organic compounds.

From the above discussions it’s clear that dye is a mixture of two or more colours and the different colours in a dye can be separated by chromatography.
So, the correct answer is “Option C”.

Note: The difference between the terms dyes and pigments should be noted. The pigments are usually referred to as oxides like chromium oxides and iron or as inorganic salts. They can be colourless or coloured or fluorescent in inorganic or organic solids which are usually insoluble and physically or chemically unaffected by the medium in which they are mixed with.