Brownian movement. When a colloidal solution is examined with an ultra-microscope, the suspended particles are seen to be in a constant rapid zig-zag motion. This constant rapid zig-zag motion of colloidal particles is known as Brownian movement after the name of the discoverer Sir Robert Brown (1827).
Fig. Brownian movement. Causes: It is due to the unequal bombardment of colloidal particles by the molecules of the dispersion medium. With increase in the size of the particles, the probabilities of unequal bombardment decreases and the Brownian movement disappears. This is why coarse suspensions do not exhibit Brownian movement.
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What are the different steps involved in a heterogeneously catalysed reaction?
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Explain the purification of colloidal solutions by dialysis and ultrafiltration.
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Some zeolites are used to separate long straight chain hydrocarbons from branched chain hydrocarbons in petrochemical industry. Explain how this separation becomes possible.
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Consider the adsorption isotherm given below and interpret the variation in the extent of adsorption (x/m) when:
(i) temperature increases at constant pressure. (ii) pressure increases at constant temperature.
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Justify the use of gelatin as a protective colloid.
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How is a colloidal solution purified by ultrafiltration?
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What is the coagulating power of an electrolyte? What is the cause of coagulation?
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Give applications of colloids in detail.
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Explain the chemical phenomenon involved in the purification of water using potash alum.