Purification (Crystallization, Sublimation, Distillation,...) NEET Questions

Organic Chemistry - Purification and Characterization of Organic Compounds

Purification (Crystallization, Sublimation, Distillation,...) MCQ Questions


1.
Crystallisation as a method of purification of solid organic compounds is based on the difference in:
A.
Vapour pressures of the compound and impurities
B.
Densities of the compound and impurities
C.
Solubilities of the compound and impurities in a suitable solvent
D.
Boiling points of the compound and impurities
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ANSWER :
C. Solubilities of the compound and impurities in a suitable solvent
2.
In the process of crystallisation, the impure compound is dissolved in a solvent in which:
A.
It is appreciably soluble at room temperature but insoluble at higher temperature
B.
It is sparingly soluble at room temperature but appreciably soluble at higher temperature
C.
It is insoluble at all temperatures
D.
It is highly soluble at all temperatures
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ANSWER :
B. It is sparingly soluble at room temperature but appreciably soluble at higher temperature
3.
Coloured impurities present in an organic compound during crystallisation are removed by adsorbing them over:
A.
Activated charcoal
B.
Anhydrous calcium chloride
C.
Alumina
D.
Silica gel
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ANSWER :
A. Activated charcoal
4.
The filtrate obtained after crystallisation is called:
A.
Sublimate
B.
Eluate
C.
Distillate
D.
Mother liquor
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ANSWER :
D. Mother liquor
5.
Repeated crystallisation is necessary when:
A.
The compound contains impurities of comparable solubilities
B.
The compound is insoluble in all solvents
C.
The compound is coloured
D.
The compound is highly volatile
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ANSWER :
A. The compound contains impurities of comparable solubilities
6.
If a compound is highly soluble in one solvent and very little soluble in another, crystallisation is carried out using:
A.
Pure water only
B.
Either solvent alone
C.
Activated charcoal
D.
A mixture of the two solvents
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ANSWER :
D. A mixture of the two solvents