--%>
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 : Isotonic Solutions Which one of the

    Which one of the following pairs of solutions can we expect to be isotonic at the same temperature:(i) 0.1M Urea and 0.1M Nacl  (ii) 0.1M Urea and 0.2M Mgcl2  (iii) 0.1M Nacl and 0.1M Na2SO4  (iv) 0.1M Ca(NO3<

    		•
  • Q : Describe Transformation Matrices. Each

    Each symmetry operation can be represented by a transformation matrix.You have seen what happens when a molecule is subjected to the symmetry operation that corresponds to any of the symmetry elements of the point group to which the molecule belongs. The m

    		•
  • Q : Describe the function of the

    Briefly describe the function of the monosaccharide?

    		•
  • 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 : Help 1) Chromium(III) hydroxide is

    1) Chromium(III) hydroxide is highly insoluble in distilled water but dissolves readily in either acidic or basic solution. Briefly explain why the compound can dissolve in acidic or in basic but not in neutral solution. Write appropriate equations to support your answer. 2) Explain how dissolving t

    		•
  • Q : Determining of normality of sodium

    Can someone please help me in getting through this problem. The normality of a solution of sodium hydroxide 100 ml of which includes 4 grams of NaOH is: (a) 0.1 (b) 40 (c) 1.0 (d) 0.4

    		•
  • Q : Electrochemistry ( electrolysis of

    1. Define Faraday's first law of electrolysis 2. define Faraday's second law of electrolysis

    		•
  • 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

    		•
  • Q : What are electromotive force in

    The main objective of this particular aspect of Physical Chemistry is to examine the relation between free energies and the mechanical energy of electromotive force of electrochemical cells. The ionic components of aqueous solutions can be treated on the basis of the

    		•
  • Q : Advantages of doing your own chemistry

    What are the advantages of doing your own chemistry assignments? State your comment?

    		•