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Question
Assertion :Gold sol is hydrophobic and multimolecular. Reason: Gold sol is prepared by Bredig's arc method.
Assertion :Gold sol is hydrophobic and multimolecular. Reason: Gold sol is prepared by Bredig's arc method.
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Solution
The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
Sols of metals e.g. gold sol, platinum sol etc. and the sols of insoluble substances such as metal sulphides and oxides are some examples of lyophilic sols.
Lyophilic sols are relatively less stable as compared to lyophilic sols. They are easily precipitated (or coagulated) on addition of small amounts of electrolytes, by heating or agitation. Moreover, the precipitated dispersed phase cannot be brought back into the sol state by simply mixing it with the dispersion medium. This is why hydrophobic sols are also known as irreversible sols.. The lyophobic sols need stabilizing agents to keep them in the sol form for a longer time. Bredig's arc method is a method of preparation of colloidal solution, of metals such as gold, silver or platinum. This method consists of both dispersion and condensation. The water is kept cold as an ice bath. The Colloidal particle prepared is stabilized by adding a small amount of KOH to it. Hence both assertion and reason are true B is answer.
Sols of metals e.g. gold sol, platinum sol etc. and the sols of insoluble substances such as metal sulphides and oxides are some examples of lyophilic sols.
Lyophilic sols are relatively less stable as compared to lyophilic sols. They are easily precipitated (or coagulated) on addition of small amounts of electrolytes, by heating or agitation. Moreover, the precipitated dispersed phase cannot be brought back into the sol state by simply mixing it with the dispersion medium. This is why hydrophobic sols are also known as irreversible sols.. The lyophobic sols need stabilizing agents to keep them in the sol form for a longer time. Bredig's arc method is a method of preparation of colloidal solution, of metals such as gold, silver or platinum. This method consists of both dispersion and condensation. The water is kept cold as an ice bath. The Colloidal particle prepared is stabilized by adding a small amount of KOH to it. Hence both assertion and reason are true B is answer.
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