[Delhi 2014] Answer/Explanation. Reversal of Charge It has already been shown in Figs. Immediate online access to all issues from 2019. By mixing two oppositely charged sols - Oppositely charged sols when mixed together in almost equal proportion, neutralise their charges and get partially or completely precipitated. For example, Fe(OH) 3 sol and gold sol. This document is highly rated by Class 12 students and has been viewed 2857 times. 3. 2 and 3 that ferric nitrate solutions strongly reverse the charge of the silver bromide sol depending on pH. (ii) Lyophobic sols (iii) Emulsions Answer: (i) Multimolecular colloids: Colloidal particles consist of aggregates of small atoms or molecules. In these methods, smaller particles of dispersed phase are condensed suitably to be of colloidal size. Describe briefly and three methods by which coagulation of lyophobic sols can be carried out. Answer: Explaination: Starch in water is lyophilic sol, whereas AS 2 S 3 in water is lyophobic sol. 2) Dispersion methods. Once the particles are separated, they cannot be incorporated back into the sols by means of simple remixing. Coagulation is generally brought about by the addition of electrolyte. In the colloidal solution of arsenious sulphide, each particle is surrounded by HS- ions, produced by the dissociation of H 2 S. Want to see this answer and more? At the same time, adding a lyophilic colloid to a lyophobic sol can slow down the coagulation process and make a kinetically stable colloidal system. For example, As 2 S 3 sol. (1) By electrophoresis: In electrophoresis the colloidal particles move towards oppositely charged electrode. However, when a lyophilic colloid is added to any lyophobic sol it becomes less sensitive towards electrolytes. Lyophobic colloids are less stable; therefore, a stabilizing agent is often used to make this system stable. Coagulation of lyophilic solutions: Stability of lyophilic sol depends on the following two factors. 1. Main Difference – Lyophilic vs Lyophobic Colloids. Double Decomposition Method: Preparation of Arsenious Sulphide Sol: Arsenious sulphide, As 2 S 3 is a lyophobic colloid. n Conde Dispersio on me nsati methods thod. EX: If equal proportions of a positively charged sol of hydrated ferric oxide and a negatively charged sol of arsenious sulphide are mixed, then the coagulation of both the sols takes place. 4. The coagulation values in millimoles per litre of the electrolyte for the coagulation of As2S3 sol are given ... Give one example each of lyophobic sol and lyophilic sol. Want to see the step-by-step answer? Question 48. Lyophilic sols Colloidal sols directly formed by mixing substances in a suitable dispersion medium are called lyophilic sols. Lyophillic colloids: It is made up of two words; ‘Lyo’ meaning liquid and ‘Phillic’ meaning loving, so those colloids which are attracted by the liquid (solvent), are called as lyophillic colloids. Dec 11, 2020 - Theory & Procedure, Preparation of Lyophilic and Lyophobic Sols Class 12 Notes | EduRev is made by best teachers of Class 12. Coagulation of lyophobic sols can be done by the following methods: By electrophoresis - The colloidal particles move towards oppositely changed electrodes get discharged and precipitate. kerish12ka4 kerish12ka4 3 hours ago Chemistry Secondary School +5 pts. Charge ; Solvation; When the above two factors are removed then only lyophilic sols can be coagulated. (ii) Boiling: On Join now. The Mechanism of Coagulation of Lyophobic Sols as Revealed Through Investigations of Silver Halide Sols in Statu Nascendi. Lyophobic sols are formed only by special methods. This can be done by either adding an electrolyte or a suitable solvent. Log in. In these sols, the particles of disperesed r phase have no affinity for dispersion medium and they are irreversible sols. These are unstable and hence, require traces of stabilizers. Lyophilic sols are more stable than the lyophobic sols. When these come in contact with the electrode for long these are discharged and precipitated. The coagulation of the lyophobic sols can be carried out by following methods. They are irreversible. 71. Name of method : The method which can be used for coagulation of lyophobic solutions is electrophoresis. Lyophilic: The lyophilic colloids are highly viscous in nature and have higher viscosity than that of the medium. (ii) Lyophobic sols: There is no affinity between dispersed phase and dispersion medium. They are prepared by indirect methods. Difference between Lyophobic and Lyophilic sol Collodial systems may also be classified as lyophobic (Solvent hating) and lyophilic (solvent loving) sols. This type of coagulation is called mutual coagulation. In sols of lyophobic colloids, the solid dispersed phase can be separated (coagulated) by adding an electrolyte or heating. The coagulation of the lyophobic sols cannot be carried out by an electroosmosis. The addition of a small amount of electrolytes causes precipitation or coagulation of lyophobic sols. Difference between Lyophilic and Lyophobic Colloids. They are prepared by special methods, e.g., Gold sol, As2S3 sol etc. Students acquire the skill to prepare lyophilic sols using starch, gum and egg albumin. The problem of the nature of the stability of colloidal solutions and the mechanism of their coagulation by electrolytes has been examined. In hydrophobic sols, coagulation can be brought about by changing the electrolyte ... = ). Students acquire the skill to prepare lyophobic sols using ferric chloride, aluminium chloride and arsenious oxide. This is done by the following methods … It depends on many factors: particles' size and concentration, process temperature, presence of electrolytes. (1) By electrophoresis: In electrophoresis the colloidal particles move towards oppositely charged electrode. 2. A colloid is a type of homogeneous mixture where the dispersed particles do not settle out. Lyophobic colloids. Examples of lyophobic colloids are metals and their insoluble compounds such as sulphides. Coagulation or Flocculation or Precipitation “The phenomenon of the precipitation of a colloidal solution by the addition of the excess of an electrolyte is called coagulation or flocculation.”. Students acquire the skill to purify the sols by dialysis method. answered what is meant of coagulation of colloidal solution? Describe two methods by which coagulation of lyophobic sol… Get the answers you need, now! Join now. In condensation method, the smaller particles of the dispersed phase are aggregated to form larger particles of colloidal dimensions. 1. Following are the three methods by which coagulation of lyophobic sols can be carried out. Thus, lyophilic colloids can prevent the coagulation of any lyophobic sol. They are reversible. Lyophobic sols are those which cannot be obtained again by the addition of a dispersion medium, once the dispersed phase is precipitated. Ask your question. Students understand the terms lyophilic sols, lyophobic sols etc. In lyophobic systems, by adding electrolytes the coagulation rate increases sharply. Ask your question. Peptizati on Mechanical Electrical dispersion Dispersion Condensation method. Theory Since particles of dispersed phase in lyophilic sols have an affinity for the particles of dispersion medium, these sols are more stable as compared to lyophobic sols. Types of preparation of. EXPERIMENT 1.1 Aim To prepare (a) lyophilic sol; and (b) lyophobic sol. Log in. It is obtained by the hydrolysis of arsenious oxide (AS 2 0 3) with boiling distilled water, followed by passing H 2 S gas through solution obtained. Method B, concentration of the ferric nitrate stock solution _>2 X 10-3 M. COAGULATION AND REVERSAL OF CHARGE OF COLLOIDS 209 B. The table below shows the main differences between Lyophilic and Lyophobic Colloids or sols: Lyophobic: The charge on lyophobic sol can be positive or negative.As 2 S 3 sol is negative in nature while Fe(OH) 3 sol is positive in nature. These are also called reversible sols. The coagulation of a lyophobic colloidal solution can be achieved by mixing two oppositely charged sols. Lyophilic sols are formed easily by direct mixing. When an electrolyte is added to the colloidal solution, the particles of the sol take up the ion which is oppositely charged and thus get neutralised. Lyophobic sols are also known as irreversible medium because on evaporating the dispersion medium cannot be readily reconverted into sols by simple methods. Name any method by which coagulation of lyophobic sols can be carried out. These are self-stabilized. What is ment by coagulation of colloidal solution ? EX: If equal proportions of a positively charged sol of hydrated ferric oxide and a negatively charged sol of arsenious sulphide are mixed, then the coagulation of both the sols takes place. Lyophobic colloids can be prepared by special methods and require a stabilising agent. Condensation Methods. These are quite stable and cannot be easily coagulated. Three methods by which coagulation of lyophobic sols can be carried out are: (i) Electrophoresis: During electrophoresis the colloidal particles move towards oppositely charged electrodes, get discharged and coagulated. check_circle Expert Answer. (All India 2010) Answer: Coagulation : The process of settling of colloidal particles is called coagulation or precipitation of the solution. Also, you will learn a method of purification of sols. Lyophobic: The Lyophobic colloids have almost same viscosity as that of medium. Check out a sample Q&A here. Name any method by which coagulation of lyophobic sols can be carried out. Following are the three methods by which coagulation of lyophobic sols can be carried out. Viscosity. These are quite stable. Lyophobic sols can be prepared by mainly two types of methods: 1) Condensation methods. Coagulation is generally brought about by the addition of electrolyte. These sols are less stable as weak forces of interaction exist between colloidal particles and liquid (dispersed phase and dispersed medium). The coagulation of the lyophobic sols can be carried out by following methods. Lyophobic sols can be easily coagulated by the addition of small quantity of an electrolyte. 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