International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

How does a chromatogram indicate the differences between various dyes?

1. Each dye has a different chemical formula

2. Each dye has a different absorption spectrum

3. Each dye has a different mixture

4. Each dye has a similar appearance

The correct answer is: Each dye has a different mixture

A chromatogram is a visual representation of the separation of different components in a mixture. When it comes to dyes, the process of chromatography highlights the fact that each dye can travel a different distance on the chromatography medium due to variations in their interaction with the stationary and mobile phases. The correct answer indicates that each dye in a mixture will show different characteristics on the chromatogram, such as distinct spots or bands appearing at different locations along the strip. This is because dyes have different properties and affinities for the stationary phase (like paper or silica gel) and the mobile phase (solvent). As the solvent moves up the medium, it carries the dyes with it, but at different rates, leading to distinct and quantifiable differences. The other options do not accurately reflect how a chromatogram operates. While it is true that each dye can have a different chemical formula or absorption spectrum, these characteristics do not directly translate to how they are represented on a chromatogram. Similarly, stating that dyes have a similar appearance contradicts the purpose of chromatography, which is to separate and identify components based on their unique properties. Hence, the observation of different spots on the chromatogram effectively demonstrates the differences in how various dyes behave in the chromatography process.