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Methods to Form Lyophobic Colloids

In lyophobic ...

Question

In lyophobic colloids how is the process irreversible though coagulation is possible?

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Solution

Dear Student, In lyophobic sols/colloids if small amount of electrolyte is added, the sols are readily precipitated and do not give back the colloid by simple addition of the dispersion medium. So they are called irreversible Colloids. Regards

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Q. Write a method by which lyophobic colloids can be coagulated.

Q. The gold number of certain lyophillic colloids is given below. Which of the following is most effective in protection of lyophobic colloids against coagulation?
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Q. What is meant by coagulation of a colloidal solution? Describe briefly any three methods by which coagulation of lyophobic sols can be carried out.

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

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^{-}

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[A g I] I^{-}

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

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

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