Q.Answer the following question.
Aqueous solution of raw sugar, when passed over beds of animal charcoal, becomes colourless. Explain.
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Start your 14-day free trial to unlock the full solution →Step 1. Identify the process. Raw (unrefined) sugar solution contains coloured impurities (organic pigments) mixed in with the dissolved sugar. Passing this solution over a bed of animal charcoal removes the colour.
Step 2. Explain the mechanism. Animal charcoal (like activated charcoal generally) is highly porous, giving it an enormous surface area per unit mass. As the sugar solution flows through/over the charcoal bed, the coloured impurity molecules are selectively adsorbed onto this large internal surface, while the dissolved sugar molecules largely pass through in solution.
Step 3. Connect to the chapter's other example. This is directly analogous to the methylene-blue example given earlier in the chapter (Section 11.2.3), where shaking charcoal with a methylene blue solution removes the colour because the dye molecules accumulate on the charcoal's surface -- both are cases of adsorption of colouring matter by charcoal. …
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