InterviewSolution
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InterviewSolution
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By the process of cystallization, we convert an impure compound into its crystals. The choice of the solvent is very crucial in this operations. Which of the following conditions must be fulfilled by the selected solvent? (i) It should not react chemically with the impure organic compund. (ii) Is should be the one in which the solid organic compound is very soluble at room temperature. (iii) The impurities should not dissolve at all in the solvent. (iv) If the impurities dissolve, they should be soluble to such an extent that they remain in the filtrate (mother liquor) upon crystallization.A. (i), (iii), (iv)B. (i), (ii), (iii)C. (i), (ii), (iv)D. (i), (ii), (iii), (iv) |
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Answer» Correct Answer - D Condition `(ii)` must be fulfilled so that excess of the organic compound is thrown out as crystals on cooling the hot solution. If the impurities are more soluble in the cold solvent than is the compound being purified, then they will almost certainly remain in the solution in the mother liquor (the residual cold solution from which the compound crystallizes). The impurities which are less soluble will also probably not be precipitate on cooling because they are unlikely to be present in sufficiently high concentration to form a saturated solution even at lower temperature. Moreover, even if some impurity is deposited with the pure compound on cooling, its proportion will be considerably less than in the original crude material, and it will be completely removed by further recrystallization. |
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