The charge on the lyophobic sol particles is due to

Options

A. electron capture by sol particles during electrodispersion of metals
B. preferential adsorption of ions from solution
C. formulation of electrical double layer
D. all of these

Answer

D

Explanation

Preferential adsorption of ions is the most accepted reason. It is believed that the charge on the colloidal particles is due to preferential adsorption of either positive or negative ions on their surface. If the particles have a preference to absorb positive ions, they acquire a positive charge and if they prefer to adsorb negative charge. For example, positive charge on ferric hydroside sol prepared by hydrolysis of ferric chloride is largely due to preferential adsorption of `Fe^(3+)` ions on the surface of particles of ferric hydroxide. The ferric ions come from ionization of ferric chloride which is always present in traces in the sol. Similarly, the negative charge on arsenic sulphide sol is due to preferential adsorption of sulphide ions on the surface of arsenic sulphide particles. The sulphide ions are furnished by ionization of hydrogen sol, ferric and not chloride ion is preferred. Simmilarly, in arsenic sulphide sol, sulphide and not hydrogen ion is prefferred.