--%>
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 : Thermodynamics 1 Lab Report I already

    I already did Materials and Methods section. I uploaded it with the instructions. Also, make sure to see Concept Questions and Thinking Ahead in the instructions that I uploaded. deadline is tomorow at 8 am

    		•
  • Q : Vapour pressure of benzene Give me

    Give me answer of this question. The vapour pressure of benzene at a certain temperature is 640mm of Hg. A non-volatile and non-electrolyte solid weighing 2.175g is added to 39.08g of benzene. The vapour pressure of the solution is 600,mm of Hg . What is the mo

    		•
  • Q : Symmetry Elements The symmetry of the

    The symmetry of the molecules can be described in terms of electrons of symmetry and the corresponding symmetry operations.Clearly some molecules, like H2O and CH4, are symmetric. Now w

    		•
  • Q : What is depression in freezing point?

    Freezing point of a substance is the temperature at which solid and liquid phases of the substance coexist. It is defined as the temperature at which its solid and liquid phases have the same vapour pressure. The freezing point o

    		•
  • Q : Sedimentation and Velocity The first

    The first method begins with a well defined layer, or boundary, of solution near the center of rotation and tracks the movement of this layer to the outside of the cell as a function of time. Such a method is termed a sedimentary velocity experiment. A

    		•
  • Q : Extensive property Choose the right

    Choose the right answer from following. Which one of the following is an extensive property: (a) Molar volume (b) Molarity (c) Number of moles (d) Mole fraction

    		•
  • Q : Vapour pressure of water Give me answer

    Give me answer of this question. 5cm3 of acetone is added to 100cm3 of water, the vapour pressure of water over the solution: (a) It will be equal to the vapour pressure of pure water (b) It will be less than the vapour pressure of pure water

    		•
  • Q : Kinds of insulators Describe all the

    Describe all the kinds of insulators which are present?

    		•
  • Q : Explain physical properties of

    . Boiling pointsThe boiling points of monohalogen derivatives of benzene, which are all liquids, follow the orderIodo > Bromo > ChloroThe boiling points of isomeric dihalobe

    		•
  • Q : Coagulation what is the meaning of

    what is the meaning of fourth power of valency of an active ion?

    		•