how does colour of light changes when it passes through a colloidal solution? does dispersion takes place before light rays of other wave length scatter?
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Explain what is observed when:
(i) a beam of light is passed through a colloidal sol.
(ii) an electrolyte, NaCl is added to hydrated ferric oxide sol.
(iii) electric current is passed through a colloidal sol.
Solution
(i) When a beam of light is passed through a colloidal sol, colloidal particles scatter light and we can see the path of light. Thus, Tyndall effect is observed.
(ii) When an electrolyte, NaCl is added to hydrated ferric oxide sol.
NaCl provides colloidal particles which coagulate oppositely charged ferric hydroxide colloidal particles bearing positive charge.
(iii) When electric current is passed through a colloidal sol, the colloidal particles move towards oppositely charged electrode, where they lose their charge and are coagulated. The process is known as electrophoresis.