Short Answer TypeWrite the dispersed phase and dispersion medium of the following colloidal systems:
(i) Smoke (ii) Milk
What are lyophilic and lyophobic colloids? Which of these sols can be easily coagulated on the addition of small amounts of electrolytes?
Write the differences between physisorption and chemisorption with respect to the following:
(i) Specificity
(ii) Temperature dependence
(iii) Reversibility and
(iv) Enthalpy change
Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate.
Physiosorption, also called physical adsorption, is a process in which the electronic structure of the atom or molecule is barely perturbed upon adsorption.
|
S. No. |
Point of difference |
Physiosorption |
Chemisorption |
|
(i) |
Specificity |
This is not specific in nature. |
This is highly specific in nature. |
|
(ii) |
Temperature dependence |
Low temperature is favourable for physisorption. It decreases with increase in temperature. |
High temperature is favourable for chemisorption. It increases with the increase in temperature. |
|
(iii) |
Reversibility |
This is reversible in nature. |
This is irreversible in nature. |
|
(iv) |
Enthalpy change |
Enthalpy of adsorption is low. |
Enthalpy of adsorption is high. |
What is meant by coagulation of a colloidal solution? Describe briefly any three methods by which coagulation of lyophobic sols can be carried out.
Define the following terms:
(i) Brownian movement
(ii) Peptization
(iii) Multimolecular colloids
Define the following terms giving an example of each:
(i) Associated colloids
(ii) Lyophilic sol
(iii) Adsorption
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