Colloids have many characteristic properties. Among this Tyndall effec

1.	Colloids have many characteristic properties. Among this Tyndall effect is an optical property and coagulation is the process of settling of colloidal particles.i) What is the Tyndall effect?ii) State Hardy Schulze rule which deals with the coagulation of colloids by the addition of an electrolyte.iii) What is a protective colloid?
Answer» i) When light passes through colloids the path of light becomes visible. This effect is called Tyndall effect. This is due to scattering of light by colloidal particles. ii) It state that ‘Thegreaterthe valency of flocculating ion, the greater will be its coagulating, flocculating or precipitating power. Note: i) In the coagulation of a positive sol, the flocculating power increases in the order Na⁺< Ba²⁺ + <AI³⁺ ii) Inthe coagulation of a negative sol, the flocculating power increases in the order Cl < S0²₄ < PO³₄ < [Fe(CN)₆]⁴ Na⁺ < Ba²⁺< AI³⁺ iii) The lyophilic particles form a layer around the lyophobic particles and thus protect the latter from electrolytes. Such colloids are called protective colloids. Eg : Gold sol can be protected by adding a little gelatin. Here, gelatin is the protective colloid.

Colloids have many characteristic properties. Among this Tyndall effect is an optical property and coagulation is the process of settling of colloidal particles.i) What is the Tyndall effect?ii) State Hardy Schulze rule which deals with the coagulation of colloids by the addition of an electrolyte.iii) What is a protective colloid?

Answer»

i) When light passes through colloids the path of light becomes visible. This effect is called Tyndall effect. This is due to scattering of light by colloidal particles.

ii) It state that ‘Thegreaterthe valency of flocculating ion, the greater will be its coagulating, flocculating or precipitating power.

Note:
i) In the coagulation of a positive sol, the flocculating power increases in the order Na⁺< Ba²⁺ + <AI³⁺
ii) Inthe coagulation of a negative sol, the flocculating power increases in the order Cl < S0²₄ < PO³₄ < [Fe(CN)₆]⁴ Na⁺ < Ba²⁺< AI³⁺
iii) The lyophilic particles form a layer around the lyophobic particles and thus protect the latter from electrolytes. Such colloids are called protective colloids.

Eg : Gold sol can be protected by adding a little gelatin. Here, gelatin is the protective colloid.

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