--%>
Assignment Help - homework help

What is adsorption and its examples.

In a liquid a solid substance a molecule present within the bulk of the substance is being attracted infirmly from all sides by the neighbouring molecules. Hence there is no bet force acting on the molecule or there are no unbalanced forces of the molecule. On the other hand, a molecule present at the surface is not attracted to other molecules form all sides because there are no neighbouring molecules above the surface. Hence, it possesses some unbalanced or residual forces. As a result of these unbalanced forces the molecules present at the liquid surfaces tend to satisfy their residual forces by attracting the molecules of other species when brought in contact with them and retaining them on the surface. This causes increase in concentration of the molecular species near the surfaces as compared to its bulk phases. This accumulation of molecular species at the surface rather than in bulk of a solid or liquid is referred to as adsorption. The molecular species or a substance which concentrates or accumulates at the surface is called adsorbate. The material on the surface of which adsorption is called adsorbent.

The adsorbate and adsorbent process of removal of an adsorbed substances from surfaces is called desorption. It is reverse of adsorption and can be brought about by reducing the pressure or by heating.

Some examples of adsorption

(i) When gases like O2, H2, CO, Cl2, NH3 or SO2, are taken in a closed vessel containing powdered charcoal. It is observed that the pressure of the enclosed vessel decreases. The gas molecules get adsorbed on the surface of charcoal.

(ii) Aqueous solution of raw sugar when passed over beds of animal charcoal becomes colourless because the colouring matter of sugar is adsorbed by the animal charcoal surface.

(iii) The air becomes dry in the presence of silica gel because water molecules get adsorbed on the surface of silica gel.

(iv) When animal charcoal is added to a solution of some organic dye (say methylene blue) and the contents are filtered after thorough shaking, it is observed that the filtrate is almost colourless. The molecules of the dye are adsorbed on the surface of animal charcoal.

The above examples clarify that the solid surfaces can hold the gas or liquid molecules because of adsorption.

   Related Questions in Chemistry

  • Q : Molar mass Select the right answer of

    Select the right answer of the question. Which is heaviest: (a)25 gm of mercury (b)2 moles of water (c)2 moles of carbon dioxide (d)4 gm atoms of oxygen

    		•
  • Q : Cations Explain how dissolving the

    Explain how dissolving the Group IV carbonate precipitate with 6M CH3COOH, followed by the addition of extra acetic acid.

    		•
  • Q : Explain Vapour Pressure Composition A

    A pressure composition diagram for a liquid vapor system can be used to show the composition of the liquid and equilibrium vapor.Vapor equilibrium data are useful in the study of distillations. It is of value to have diagrams showing not only the vapor pre

    		•
  • Q : Basicity order order of decreasing

    order of decreasing basicity of urea and its substituents

    		•
  • Q : Finding strength of HCL solution Can

    Can someone please help me in getting through this problem. 1.0 gm of pure calcium carbonate was found to require 50 ml of dilute  HCL for complete reaction. The strength of the HCL  solution is given by: (a) 4 N  (b) 2 N  (c) 0.4 N  (d) 0.2 N

    		•
  • Q : What are heterogenous catalysis? Give

    When the catalyst exists in a different phase than that of reactants, it is said to be heterogeneous catalyst, and the catalysis is called heterogeneous catalysis. For example, SO2 can be oxidized to SO3

    		•
  • Q : What is Spectroscopy? This is a very

    This is a very important aspect of Physical Chemistry in which knowledge of the size, shape, rigidity and electronic structure of molecules deduced from the experimental methods treated here goes hand in hand with the theoretical approaches of chemical reactions. Spec

    		•
  • Q : Problem based on molarity Select the

    Select the right answer of the question. If 18 gm of glucose (C6H12O6) is present in 1000 gm of an aqueous solution of glucose, it is said to be: (a)1 molal (b)1.1 molal (c)0.5 molal (d)0.1 molal

    		•
  • Q : Changes in matter law of chemical

    changes in matter law of chemical combination

    		•
  • Q : Describe physical adsorption and its

    When the forces of attraction existing between adsorbate and adsorbent are van der Waal's forces, the adsorption is called physical adsorption. This type of adsorption is also known as physisorption or van der Waal's adsorption. Since the forces existing between adsorbent and adsorbate are very w

    		•