Which one of the following is not an application of adsorption?

The correct answer is Option (3) → Homogeneous catalysis

Adsorption is the gathering of molecules at a surface, the boundary between two phases. In homogeneous catalysis the reactants and the catalyst are in the same phase (all gases or all in solution), so there is no surface on which adsorption can take place. Adsorption explains heterogeneous catalysis instead, for example iron in the Haber process.

• Option (1) Separation of inert gas — An application of adsorption. Noble gases are adsorbed to different extents on coconut charcoal at different temperatures, so they can be separated.

• Option (2) In curing diseases — An application of adsorption. Many drugs act by being adsorbed on germs and killing them.

• Option (3) Homogeneous catalysis — Not an application of adsorption. Reactants and catalyst are in one phase, so there is no surface for adsorption.

• Option (4) Chromatographic analysis — An application of adsorption. Adsorption chromatography separates a mixture because its components are adsorbed to different extents on the adsorbent.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Separation of Inert Gases – “Due to the difference in degree of adsorption of gases by charcoal, a mixture of noble gases can be separated by adsorption on coconut charcoal at different temperatures.”

Homogeneous Catalysis – “When the reactants and the catalyst are in the same phase (i.e., liquid or gas), the process is said to be homogeneous catalysis.”