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(a) Write a note of Dialysis. (b) What is the effect on Delta H and Delta S during the process of adsorption ? (c ) Give an example for heterogeneous catalysis. |
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Answer» Solution :(a) It is a process of removing a dissolved substance [electrolyte] from a collodial solution by means by diffusion through a SUITABLE semipermeable membrane. Example : Parchment Or cellophane (b) `Delta H = -ve` Or `Delta H` decreases Or `Delta H lt 0` `Delta S = -ve` Or `Delta S` decreases or `Delta S lt 0` (c ) `N_(2)(g) + 3H_(2)(g) overset(Fe(s))rarr 2NH_(3)(g)` or Haber.s process `2SO_(2)(g) + O_(2) overset(Pt(s))rarr 2SO_(3)(g)` Or CONTACT process Alkene(g) `+H_(2)(g)overset(Ni(s))rarr` Alkane Or hydrogenation Oil `+ H_(2)(g) overset(Ni(s))rarr` Vanaspathi or hydrogenation `4NH_(3)(g) + 5O_(2)(g) underset("500 K, 9 bar")overset("Pt/Rh gauge catalyst")rarr 4NO(g) + 6H_(2)O(g)` `CO(g) + 3H_(2)(g) overset(Ni(s))rarr CH_(4)(g)` `CO(g) + H_(2)(g) overset(Cu(s))rarr HCHO(g)` (a) Dialysis is the treatment that does some of the tings done by healthy kidneys. Dialysis works on the principles of diffusion of solute and ultafiltration of fluid across membrane. The process used to remove waste and extra fluid from the blood. The filtered blood then returned to the body with the help of dialysis machine. (b) effect on `Delta H` and `Delta S` during process of adsorption are as follows : (i) `Delta H` is the enthalpy of adsorption i.e. heat released during the adsorption, means it is an exothermic process. For physical adsorption, it has small `-Delta H` value (about 20-40 kJ/mol), while for chemical adsorption it has larger (-) ve `Delta H` value (about 80-240 kJ/mol). (ii) Entropy is the randomness. `Delta S` is entropy change during adsorption. As the molecule adheres to the surface, the residual force decreases and movement is RESTRICTED, so the value of `Delta S` also decreases. (c ) Example of Heterogeneous catalysis : The catalytic process , in which reactant and the catalyst are in different phases is known as Heterogeneous catalysis. Oxidation of `SO_(2)` into `SO_(3)` in presence of Pt or `V_(2)O_(5)` as catalyst in contact process for manufacture of `H_(2)SO_(4)` is an example of Heterogeneous catalysis. Here reactant is in gaseous state while catalyst is in SOLID state. `2SO_(2)(g)+O_(2)(g)underset("(Solid-catalyst)")overset("Pt or " V_(2)O_(5))rarr 2SO_(3)(g)` |
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