Which of the following is/are application(s) of adsorption?

Options

A. Adsorption indicators
B. Thin layer chromatography
C. Qualitative analysis
D. All of these.

Answer

To determine which of the following are applications of adsorption, we need to analyze each option provided:

1. **Adsorption Indicators**:
- Adsorption indicators are substances that change color when they adsorb onto a solid surface, typically used in titrations. For example, silver halides can form a precipitate in a solution, and dyes like fluorescein or eosin can produce a characteristic color at the endpoint of a titration. This indicates that adsorption is indeed involved in the functioning of these indicators.

2. **Thin Layer Chromatography (TLC)**:
- TLC is a technique used for separating non-volatile mixtures. It is based on the principle of adsorption, where different components of the mixture adhere to the stationary phase (the solid) to different extents, allowing for separation. Thus, TLC is a clear application of adsorption.

3. **Qualitative Analysis**:
- Qualitative analysis often involves methods that rely on adsorption to identify substances based on their interaction with a solid phase. Techniques such as chromatography, which is a form of qualitative analysis, depend on the adsorption process to separate and identify compounds.

4. **All of These**:
- Since all the previous options (adsorption indicators, thin layer chromatography, and qualitative analysis) are valid applications of adsorption, this option encompasses all the correct applications.

### Conclusion:
Based on the analysis, the correct answer is **Option 4: All of these**.