What are lyophilic and lyophobic colloids? Which of these sols can be easily coagulated on addition of small amounts of electrolytes?

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Lyophobic colloids: These are the colloidal solution in which dispersed phase has very little affinity for the dispersion medium. Lyophilic colloids, the precipitations of lyophobic colloids do not regain their properties. These sols are formed by substances like gums, starch and proteins. Lyophilic sol can be easily prepared by directly mixing colloid with the liquid.Hence, Lyophilic Sols are very stable and do not precipitate/coagulate easily. However addition of very large quantities of electrolytes can cause particles to precipitate.

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What are lyophilic and lyophobic colloids? Which of these sols can be easily coagulated on the addition of small amounts of electrolytes?

Q. Which of the following statements are correct?
1. The smaller the gold number of lyophobic colloid, the larger will be its protective power.
2. Lyophilic sols, in contrast to lyophobic sols are easily coagulated on the addition of small amounts of electrolytes.
3. Ferric chloride solution is used to stop bleeding from a fresh cut because it coagulates the blood.
4. The flocculation value of arsenious sulfide sol is independent of the anion of the coagulating electrolyte.

Q. Lyophilic colloidal sols are much more stable than lyophobic colloidal sols. This is due to the extensive solvation of lyophilic colloidal sols, which form a protective layer outside it which prevents it from forming associated colloids. Lyophilic colloidal sols also protect lyophobic colloidal sols from precipitation by the action of electrolytes. This is due to the formation of a protective layer by the lyophilic sols outside lyophobic sols. Lyophilic sols are also called protective sols.
Gelatin (lyophilic) protects gold sol (lyophobic) from coagulation on the addition of a solution of sodium chloride. The protective powers of different colloidal sols are measured in terms of gold number.
Gold number is defined as the amount of protective sol in milligrams that prevents the coagulation of 10 mL of a given gold sol on adding 1 mL of a

10 %

solution of sodium chloride. Thus, the smaller the gold number of a lyophilic sol, the greater is the protective power.

[A g I] I^{-}

colloidal sol can be coagulated by the addition of a suitable cation. 1 mol

[A g I] I^{-}

requires

A g N O_{3}, P b (N O_{3})_{2}

F e (N O_{3})_{3}

as (in moles):

Q. What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?

Which of the following is/are correct ?
i) lyophobic sols are less stable
ii) lyophilic sols are reversible
iii) lyophobic sols are coagulated by adding electrolytes
iv) lyophobic sols are more hydrated

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