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(a) Heat of adsorption is greater for ch...

(a) Heat of adsorption is greater for chemisorptions than physisorption. Why ?
(b) What is collodion?
(c) Differentiate between peptisation and coagulation.

Text Solution

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(a) In chemisorption, chemical bonds are present in the particles of adsorbate and adsobent. As a result, attractive forces are more in chemisorption that in physisorption in which the attractive forces are only van der Walls' forces. Therefore, heat of chemisorption is more than that of physisorption.
(b) A four percent solution of cellulose nitrate prepared in a liquid mixture of ethyl alcohol and dienyhyl ether (or simply ether) is known for as colloidion.
(c ) As a result peptisation, a precipitate gets coverted into colloidal sol. Coagulation is reverse in the sense that it converts a colloidal sol into precipitate. For details, consult section 23.
For details about peptisation, consult Section 10 For details about coagulation, consult Section 23.
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Knowledge Check

  • The correct statement(s) pertaining to the adsorption of a gas on a solid surface is(are) (i) adsorption is always exothermic (ii) physisorption may transform into chemsisorption transform into chemisorption at high temperature (iii) physisorption increases with increasing temperature but chemisorption decreases with increasing temperature . (iv) chemisorption is more exothermic than physisorption , however it is very slow due to higher energy of activation.

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    A
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