- Crude products prepared in the laboratory may contain impurities, so crystallization is needed to purify the product. Crystallization involves dissolving the crude product in a suitable solvent to form crystals of the pure compound. - Aspirin is prepared by reacting salicylic acid with acetic acid and acetic anhydride. To separate aspirin, the reaction mixture is added to cold water, causing aspirin to precipitate out as crystals while other products remain in solution. - To obtain a compound that is soluble in both water and chloroform from an aqueous layer, the aqueous solution can be mixed with carbon tetrachloride. This forms two immiscible layers that can be separated,

1. Malik Xufyan
Malik Xufyan --------------------------------------
2nd
Chapter Exercise Short Questions (Fsc Part 1)
Q.4. Why is there a need to crystallize the crude product?
Ans:
When a compound is prepared in laboratory, it may contain impurities.
This impure and un-refined compound is called crude product.
It is necessary to purify the crude product. So there is a need t
product from suitable solvent.
Q.5. A water insoluble organic compound aspirin is prepared by the reaction of salicylic
acid with a mixture of acetic acid and acetic anhydr
from the reaction mixture?
Ans:
A water insoluble organic compound aspirin is prepared by the reaction of salicylic acid with
a mixture of acetic acid and acetic anhydride.
Dring aspirin preparation , when reaction mixture is added inwater , aspirin is precipitated.
Aspirin is separated from reaction mixture is added to cold water.
The aspirin forms crystals and other products remain in soluti
from water by sintered glass crucible.
Q.6. A solid organic compound is soluble in water as well as in chloroform. During its
preparation, it remains in aqueous layer. Describe a method to obtain it from this layer.
Ans:
The organic compound can be extrac
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Chapter Exercise Short Questions (Fsc Part 1)
Malik Xufyan
Q.4. Why is there a need to crystallize the crude product?
When a compound is prepared in laboratory, it may contain impurities.
refined compound is called crude product.
necessary to purify the crude product. So there is a need to crystallize the crude
product from suitable solvent.
Fig Crystallization Procedure
Q.5. A water insoluble organic compound aspirin is prepared by the reaction of salicylic
acid with a mixture of acetic acid and acetic anhydride. How will you separate the product
A water insoluble organic compound aspirin is prepared by the reaction of salicylic acid with
a mixture of acetic acid and acetic anhydride.
Dring aspirin preparation , when reaction mixture is added inwater , aspirin is precipitated.
Aspirin is separated from reaction mixture is added to cold water.
The aspirin forms crystals and other products remain in solution. Finally aspirin is filtered
from water by sintered glass crucible.
Fig . Gooch Grucible
Q.6. A solid organic compound is soluble in water as well as in chloroform. During its
preparation, it remains in aqueous layer. Describe a method to obtain it from this layer.
The organic compound can be extracted by solvent extraction.
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www.onlychemistrydiscussion.blogspot.com
Chapter Exercise Short Questions (Fsc Part 1)
When a compound is prepared in laboratory, it may contain impurities.
o crystallize the crude
Q.5. A water insoluble organic compound aspirin is prepared by the reaction of salicylic
ide. How will you separate the product
A water insoluble organic compound aspirin is prepared by the reaction of salicylic acid with
Dring aspirin preparation , when reaction mixture is added inwater , aspirin is precipitated.
on. Finally aspirin is filtered
Q.6. A solid organic compound is soluble in water as well as in chloroform. During its
preparation, it remains in aqueous layer. Describe a method to obtain it from this layer.

2. Malik Xufyan
Malik Xufyan --------------------------------------
A solid organic compound is soluble in water as well as in chloroform. During its
preparation, it remains in aqueous layer
Example:
The aqueous solution of compound is mixed with carbon tetrachloride (CCl4).
The mixture is put into the separating funnel.
Here two layers are formed. The water layer is separated and evaporated to get the
compound.
Q.7. The following figure shows a developed chromatogram on paper with five spots. (i)
Unknown mixture X (ii) Sample A (iii) Sample B (iv) Sample C (v) Sample D
Find out (i) the composition of mixture X (ii) which sample is impure & what is its
composition.
Ans:
The unknown mixture X contains the components B and C. The sample D is impure.
It contains components A and C.
We should know that a pure sample give only one spot. The samples A and C are
pure.
Q.8. In solvent extraction technique, why repeated extraction using
solvent are more efficient than using a single extraction but larger volume of solvent
Ans:
The solvent extraction technique is based upon distribution coefficient.
The ratio of concentration of a solute dissolved in two immiscible solv
It is called distribution coefficient.
K = Cocen. Of a component in the moving phase/ Concen.
In repeated extractions, we can get maximum amount of solute from the other solvent.
It is the reason that repeated extractions using small portions of solvent are more
efficient than using a singl
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A solid organic compound is soluble in water as well as in chloroform. During its
preparation, it remains in aqueous layer.
The aqueous solution of compound is mixed with carbon tetrachloride (CCl4).
The mixture is put into the separating funnel.
Here two layers are formed. The water layer is separated and evaporated to get the
owing figure shows a developed chromatogram on paper with five spots. (i)
Unknown mixture X (ii) Sample A (iii) Sample B (iv) Sample C (v) Sample D
Find out (i) the composition of mixture X (ii) which sample is impure & what is its
known mixture X contains the components B and C. The sample D is impure.
It contains components A and C.
We should know that a pure sample give only one spot. The samples A and C are
Q.8. In solvent extraction technique, why repeated extraction using small portions of
solvent are more efficient than using a single extraction but larger volume of solvent
The solvent extraction technique is based upon distribution coefficient.
The ratio of concentration of a solute dissolved in two immiscible solv
It is called distribution coefficient.
component in the moving phase/ Concen. Of that component in the stationary phase
In repeated extractions, we can get maximum amount of solute from the other solvent.
It is the reason that repeated extractions using small portions of solvent are more
efficient than using a single extraction but larger volume of solvent.
Fig. Solvent Extraction Instrument
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A solid organic compound is soluble in water as well as in chloroform. During its
The aqueous solution of compound is mixed with carbon tetrachloride (CCl4).
Here two layers are formed. The water layer is separated and evaporated to get the
owing figure shows a developed chromatogram on paper with five spots. (i)
Unknown mixture X (ii) Sample A (iii) Sample B (iv) Sample C (v) Sample D
Find out (i) the composition of mixture X (ii) which sample is impure & what is its
known mixture X contains the components B and C. The sample D is impure.
We should know that a pure sample give only one spot. The samples A and C are
small portions of
solvent are more efficient than using a single extraction but larger volume of solvent?
The solvent extraction technique is based upon distribution coefficient.
The ratio of concentration of a solute dissolved in two immiscible solvents is a constant.
in the stationary phase
In repeated extractions, we can get maximum amount of solute from the other solvent.
It is the reason that repeated extractions using small portions of solvent are more
e extraction but larger volume of solvent.