Tag: methods of purification of organic compounds

Questions Related to methods of purification of organic compounds

Which of the following is not an exact differential?

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. $dq$

  2. $dG$

  3. $d(\bar { V } )$

  4. $dS$

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Correct Option: A
Explanation:
Exact differential are those function if 
$\cfrac { \delta  }{ \delta T } (\cfrac { \delta f }{ \delta P } )=\cfrac { \delta  }{ \delta P } (\cfrac { \delta f }{ \delta T } )$ where f is the function of P and T. increase of q, it will not be equal , so it will be not exact function.

A substance which decomposes at or below its boiling point cannot be purified by?

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Steam distillation

  2. Simple distillation

  3. Fractional distillation

  4. Distillation under reduced pressure

Show answer
Correct Option: A,B,C
Explanation:

Steam distillation is used for natural aromatic compounds which are immiscible in water.
Simple and fractional distillation uses the property of difference in the boiling point. These techniques can not be used for the substance which decomposes at or below its boiling point.
Distillation under reduced pressure is basically Vaccum distillation. This method is used to boil such substances without their decomposition

Option A, B and C are the answer.

Component of urine can be separated by________.

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. distillation

  2. filtration

  3. sedimentation

  4. decantation

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Correct Option: A
Explanation:

Due to the difference between the boiling point of components, distillation can be used for separation.

An organic liquid vaporizes at a temperature _________ its boiling point in steam distillation.

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. above

  2. below

  3. equal to

  4. none of the above

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Correct Option: B
Explanation:

In steam distillation, the mixture boils when the sum of vapour pressures of water and the organic liquid becomes equal to the atmospheric pressure. Since the vapour pressure of water is appreciably higher than that of the organic liquid, it vaporizes at a temperature much lower than its normal boiling point. 

In this way, many organic compounds insoluble in water can be purified at a temperature well below the point at which decomposition occurs. 

In the destructive distillation of coal, at 443-503 K temperature, a middle oil or carbolic oil fraction is obtained. This fraction contains :

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Phenol

  2. Xylenes

  3. Naphthalene

  4. Benzene

Show answer
Correct Option: A,C
Explanation:

 (3) Distillation of coal tar : Arenes are isolated by fractional distillation of coal tar,

Table : 

Name of the fraction

Temperature range (K)

Main constituents

Light oil (or crude oil) fraction
Middle oil fraction (Carbolic oil)
Heavy oil fraction (Creosote oil)
Green oil (Anthracene oil)
Pitch (left as residue)

 So at 443-503 K temperature phenol and naphthalene is formed

Hence options A & C are correct.

Which of the following procedures will give you water free from all impurities?

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. Adding chlorine tablets

  2. Distillation

  3. Boiling

  4. Filtration

Show answer
Correct Option: B
Explanation:

Distillation procedures will give us water free from all impurities. The distillation process removes almost all impurities from water. Distillers are commonly used for removing nitrate, bacteria, sodium, hardness (dissolved solids), most organic compounds, heavy metals and radionuclides from water. Distillers remove about 99.5% of the impurities from the original water.

The fragrance of the flower is due to the presence of some steam volatile organic compounds called essential oils. These are generally insoluble in water at room temperature but are miscible with water vapour in the vapour phase. A suitable method for the extraction of these oil from the flower is:

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. distillation

  2. crystallisation

  3. distillation with reduced pressure

  4. steam distillation

Show answer
Correct Option: D
Explanation:

As the component is miscible with water vapour in vapour phase so steam distillation will be most suitable method for extraction.

Glycerin can be purified by:

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. vacuum distillation

  2. simple distillation

  3. steam distillation

  4. fractional distillation

Show answer
Correct Option: A
Explanation:
The liquids which decompose at its boiling point can be purified by vacuum distillation. Glycerol decomposes at its boiling point (563K). It can be distilled by vacuum distillation without decomposition at 453K and under 12mm Hg pressure.

Distillation under reduced pressure is generally used to purify those liquid which:

chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

  1. have very low boiling points

  2. are volatile

  3. have high boiling points and which decompose below their boiling points

  4. have a large difference in their boiling points.

Show answer
Correct Option: C