Which of the following condensation methods is used to prepare colloidal solution of arsenious sulphide?

Options

A. Double decomposition
B. Oxidation
C. Reduction
D. Hydrolysis

Answer

A

Explanation

Lypophobic sols can be prepared by two types of methods: condensation methods and dispersion methods. In condensation methods, particles of atomic or molecular size are induced to combine to form aggregates having colloidal dimensions. For this purpose chemical as well as physical methods can be applied.
In chemical methods, colloidal solutions are prepared by chemical reactions leading to formation of molecules by double decomposition (for compounds), oxidation (foro hydroxides). These molecules then aggregate leading to formation of sols:
`As_(2)O_(3)+3H_(2)Soverset("Double decomposition")(rarr)As_(2)S_(2)(sol.)+3H_(2)O`
`SO_(2)+2H_(2)Soverset("Oxidation")(rarr)3S(sol.)+2H_(2)O` .
`2AuCl_(3)+3HCHO+3H_(2)Ooverset("reduction")(rarr)`
`2Au(sol)+3HCOOH+6HCl`
`FeCl_(3)+3H_(2)Ooverset("Hydrolyris")(rarr)Fe(OH)_(3)(sol.)+3HCl`