State whether the following statements are True or False. Also, correct the False statements. Class 9

State whether the following statements are True or False. Also, correct the False statements. Class 9

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Question 1.

State whether the following statements are True or False. Also, correct the False statements. Class 9

(i) Salt can be separated from a salt solution by evaporation or distillation.

(ii) Distillation can be used for separation of two liquids even when these have the same boiling point.

(iii) In paper chromatography, the solvent level should be above the sample spot at the beginning of the experiment.

(iv) Evaporation and crystallization are the same processes.

Answer:

(i) True. Salt can be separated from salt solution by evaporation (the water evaporates, leaving salt behind). Distillation can also be used if we want to recover the water as well.

(ii) False. Distillation works only when the two liquids differ in boiling points (by at least about 25°C). If two liquids have the same boiling point, they cannot be separated by distillation.

(iii) False. In paper chromatography, the solvent level should be below the sample spot. If the solvent level is above the spot, the sample will dissolve directly into the solvent instead of being carried up the paper by capillary action.

(iv) False. Evaporation is the process of removing the solvent by heating, leaving the solute behind (but may not give pure crystals). Crystallization is a more precise process that gives pure crystals of the solute by controlled cooling of a saturated solution. Crystallization gives purer and better-formed crystals than simple evaporation.