Question

Which of the following is application of adsorption in chemical analysis?
(A) Adsorption indicators
(B) Thin layer chromatography
(C) Qualitative analysis
(D) All of these.

Answer 1

Hint: When the gas molecules or atoms are held to the solid surface by chemical bonds, the adsorption is termed as chemical adsorption or chemisorption. The chemical bonds may be covalent or ionic in nature. Chemisorption has rather high energy of activation and is, therefore, often referred to as activated adsorption.

Complete answer:
> Various applications of adsorption are production of high vacuum. The remaining traces of air can be absorbed by charcoal from a vessel evacuated by a vacuum pump to give a very high vacuum.
> Gas masks: Gas mask consists of activated charcoal or mixture of adsorbents is usually used for breathing in coal mines to adsorb poisonous gases.
> Removal of colouring matter from solutions: Animal charcoal removes colours of solutions by absorbing coloured impurities.
> Adsorption indicators: Surfaces of certain precipitates such as silver halides have the property of absorbing some dyes like eosin, fluorescein, etc. thereby producing a characteristic colour at the end point.
> Chromatographic analysis: Chromatographic analysis based on the phenomenon of adsorptions finds a number of applications in analytical and industrial fields. Thin layer chromatography is based on adsorption. Adsorption finds its application in Qualitative analysis also.

Hence the correct answer is (D).

Note: The chemical adsorption initially with increase in temperature but after some time it will decrease with increase in temperature. It also depends upon surface area. It increases with increase of surface area and chemical adsorption cannot be reversible.