How is crystal of pure substances are obtained?
(A)Crystallization.
(B)Chromatography.
(C)Peptization.
(D)All of these.
The correct answer is (A) Crystallization. Crystallization is a process through which crystals of a pure substance are obtained. It involves the conversion of a solid, liquid, or gas into a crystal lattice structure through the cooling or evaporation of a solution containing the substance.
To obtain crystals of a pure substance through crystallization, you can follow these general steps:
1. Dissolve the substance: Start by dissolving the pure substance in a suitable solvent. The solvent should be capable of dissolving the substance at a higher temperature but should allow it to crystallize when cooled or evaporated.
2. Purify the solution: If the initial solution contains impurities, you can purify it by filtering it to remove any solid particles or by performing additional separation techniques like chromatography if necessary.
3. Cooling or evaporation: After obtaining a purified solution, you can induce crystallization by either cooling the solution or allowing it to evaporate slowly. Both methods reduce the solubility of the substance, causing it to come out of the solution and form crystals.
4. Isolate the crystals: Once crystals have formed, separate them from the remaining solution. This can be achieved through several techniques like filtration, centrifugation, or decantation.
Overall, crystallization is an effective method for obtaining crystals of pure substances and is commonly used in various fields, including chemistry, geology, and materials science.