a) Name the above two methods of preparation of ferric hydroxide sol. b) What happens when an electric potential is applied across

Question

Ferric hydroxide sol can be prepared from freshly prepared ferric hydroxide precipitate. It can also be prepared by adding ferric chloride solution to boiling water. In both cases the sol particles are positively charged. 

a) Name the above two methods of preparation of ferric hydroxide sol.

b) What happens when an electric potential is applied across two platinum electrodes dipping in ferric hydroxide sol? Explain.

Answer 1

a) The method of preparation of ferric hydroxide sol from freshly prepared ferric hydroxide precipitate is called peptization. The method of preparation of ferric hydroxide sol by the addition of ferric chloride solution to boiling water is called hydrolysis,

b) When an electric potential is applied across two platinum electrodes dipped in ferric hydroxide sol electrophoresis will occur. Since ferric hydroxide sol is positively changed the colloidal particles will move towards the platinum electrode which acts as the cathode (negative electrode).