(a) How is Gold-sol prepared by Bredig’s-arc method?
(b) What is Homogeneous catalysis? Give an example.

Explanation

(a)

An electric arc is struck between electrodes of the metal immersed in the dispersion medium. the heat produced vapourises the metal which condenses to form particles of colloidal size.
(i) (i) + Electrodes
An electric arc is struck between electrodes of the metal immersed in the dispersion medium. The heat produced vapourises the metal which condenses to form particles of colloidal size.
(ii)At catalytic process in which reactant and the catalyst are in the same phase, then the process is called homogeneous catalysis.
Example (1): Oxidation of sulphur-di-oxide to sulphur trioxide.
`2SO_(2)(g) + O_(2)(g) overset(NO(g))(to) 2SO_(3) (g)`
NO is a catalyst. .
Example (2) : Acid hydrolysis of methylacetate
`CH_(3)COOCH_(3)(l) + H2O(l) overset(HCI(l))(to) CH_(3)COOH(aq) + CH_(3)OH(aq)`
Example (3) : Acid hydrolysis of canesugar
`CO(aq) + H_2O(l) overset(H^(+))(to) underset(G"lucose")(C_(6)H_(12)O_(6))(aq) + underset(F"ructos"e)(C_(6)H_(12)O_(6)(aq)`.
(c)Entropy decreases.