Question

Question #2e313

Answer 1

You can prepare a colloidal solution of gold by reducing its salts in basic solutions with agents such as formaldehyde.

Explanation:

A typical reaction is

`underbrace("2AuCl"_3"(aq)")_color(red)("gold(III) chloride") + underbrace("3HCHO(aq)")_color(red)("formaldehyde") + "9OH"^"-""(aq)" → underbrace("2Au(s)")_color(red)("gold sol") + underbrace("3HCOO"^"-""(aq)")_color(red)("formate ion") + "6Cl"^"-""(aq)" + "6H"_2"O(l)"`

The colloidal gold particles remain in suspension for about ten days without using any stabilizing agent.