Exercise 5.6
Filter the crystals, rinse them with cold water and allow them to dry on a watch glass (Fig. 5.8d).
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
(i) True. Evaporation drives the water off and leaves the salt behind; distillation does the same and also recovers the water, since a liquid can be distilled out of a solution containing a dissolved solid, the solid staying in the distillation flask.
(ii) False. Corrected: Distillation can separate two liquids only when their boiling points differ by at least about $\displaystyle 25$ °C. If the boiling points are the same, both liquids vaporise together and the distillate is still a mixture.
(iii) False. Corrected: In paper chromatography, the solvent level should be below the sample spot at the beginning of the experiment. If the solvent covered the spot, the ink would simply dissolve away into the liquid instead of being carried up the paper.
(iv) False. Corrected: Evaporation and crystallization are different processes. In evaporation the solvent is driven off and lost, and any soluble impurity stays behind with the solid; in crystallization a hot saturated solution is cooled slowly so that the pure substance separates as crystals, leaving impurities in the solution.