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प्रश्न
Describe some chemical reactions which lead to the formation of colloidal solutions.
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उत्तर
1. Double Decomposition Reactions: When two soluble salts are mixed and an insoluble substance (precipitate) is formed, it may form a colloidal sol if the particles are in the colloidal size range.
\[\ce{As2O3 + 3H2S -> 2As2S3 (Colloidal) + 3H2O}\]
2. Oxidation Reactions: In these reactions, a sol is formed due to oxidation of a substance.
\[\ce{SO2 + 2H2S -> 3S (Colloidal) + 2H2O}\]
Here, sulfur is precipitated in the colloidal form.
3. Reduction Reactions: Soluble salts of metals are reduced to their respective metals in colloidal form.
\[\ce{AuCl3 + 3 HCHO + 3H2O -> Au (Colloidal) + 3HCOOH + 3HCl}\]
4. Hydrolysis Reactions: Certain salts undergo hydrolysis to give rise to colloidal solutions.
\[\ce{FeCl3 + 3H2O -> Fe(OH)3 (Colloidal) + 3HCl}\]
These reactions are widely used in laboratories and industries to prepare colloidal solutions of various substances like arsenic sulfide, ferric hydroxide, gold, and sulfur.
