Question
(a) What is gel? Give an example.
(b) How is gold sol prepared by reduction method ?
Solution
Answer:
(a) Gel is a colloidal solution of liquid in a solid, i.e., liquid is dispersed phase and solid is the dispersion medium. A gel is a semi-solid which melts on heating. Examples of gels are: Thin jellies, gum arobic, processed cheese, silicic acid.
(b) It is prepared by reduction of gold chloride (AuCl3) solution with stannous chloride
2AuCl3 + 2SnCl → 3SnCl4 + 2Au
(Violet gold sol.)
