Tag: organic chemistry : some basic principles and techniques

Questions Related to organic chemistry : some basic principles and techniques

The best solvent for the crystallization of organic solid is in which:

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

  1. organic compound is highly soluble

  2. compound is soluble on warming

  3. compound is soluble at $90^{0}$

  4. compound is insoluble

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Correct Option: B
Explanation:

Generally speaking you need to take polar solvents for polar compound and nonpolar solvents for nonpolar compounds. Many times a mixture of solvents works better. Once you have this basic idea, crystallization is a skill developed over a period of time by trial and error process. Even after long experience you may not hit the right solvent in the first try.

In fractional distillation of petroleum, the vapours with highest boiling point ____________.

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

  1. condense in upper most portion'

  2. condense in lower most portion

  3. condense in middle portion

  4. none of these

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Correct Option: B
Explanation:

The fractional column is hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top.

Which of the following method is used for the purification of solids?

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

  1. Distillation under reduced pressure

  2. Distillation

  3. Steam distillation

  4. Sublimation

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Correct Option: D
Explanation:

Sublimation is the process in which solid gets converted into vapours directly without passing through the liquid state.

Which of following is incorrectly matched?

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

  1. Distillation - Liquids stable at their boiling point

  2. Distillation under reduced pressure - Liquids that decompose at their boiling point

  3. Steam distillation - Liquids that are immiscible with water

  4. All are true

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Correct Option: D

There is a mixture of three solid compounds A, B and C. Out of these compounds A and Care soluble in water and compound C is sublimable also. In what sequence the following techniques can be used for their effective separation? 
I. Filtration
II. Sublimation
IIl. Crystallisation from water extract
IV. Dissolution in water

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

  1. (II), (I), (IV), (III)

  2. (IV), (I), (II), (III)

  3. (I), (II), (III), (IV)

  4. (II), (IV), (I), (III)

Show answer
Correct Option: D
Explanation:

Sublimation will separate C from A and B. On adding water, A will dissolve but B will not. B can be separated by filtration. A will be present in the filtrate and can be obtained by crystallisation from water extract.

What cant be removed after distillation of water?

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

  1. Suspensions

  2. Precipitates

  3. Volatile liquids like alcohol

  4. Dissolved salts

Show answer
Correct Option: C
Explanation:

Distillation is the process of purifying water by removing contaminants.

A volatile liquid has a comparatively smaller boiling point than the water thus it becomes difficult to separate them. 

Silt in water remains suspended. It is removed by sedimentation and filtration. For increasing its sedimentation aluminium sulphates and calcium hydroxide (slaked lime) are added. As a result sticky aluminium hydroxide.

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

  1. Destroys slit particles

  2. Attracts the particles of slit

  3. Mixes with slit particles

  4. Makes slit particles increases in size and deposit at the bottom

Show answer
Correct Option: B
Explanation:

The silt in $H _2O$ remains suspended. To attract some more silt particles, $Al(OH) _3$ is used. It is used to absorb the silt particles and make the liquid more pure.

Which of the following is a physico-chemical method of separation and purification?

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

  1. Electrolysis

  2. Distillation in a flask or a big tower

  3. Filtration through a filtering medium

  4. Leaching

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Correct Option: A
Explanation:

Electrolysis is the only physico-chemical method. Rest all are physical processes.

Refining of petroleum does not involve.

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

  1. Simple distillation

  2. Steam distillation

  3. Fractional distillation

  4. Distillation under reduced pressure

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

The steam distillation process works on the principle that when a mixture of two or more undissolved liquids are heated, while ensuring that the surfaces of both liquids are in contact with the atmosphere, the vapor pressure exerted by the system increases. This method is used for the refining of petroleum. 


So, simple distillation, fractional distillation, distillation under reduced pressure are not involved in the refining of petroleum.

Options A, C, and D are correct answers.

Select the correct code by matching list I and list II.


 List -I    List -II
A) Fractional Distillation a) A liquid having sufficiently different boiling points
 B) Fractional Crystallization b) Solids having different solubilities
 C) Vacuum Crystallization c) A liquid that decomposes at its boiling point
 D) Solvent extraction d) Liquids of almost same boiling points

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

  1. A - a, B - b, C - c, D - d

  2. A - a, B - c, C - b, D - d

  3. A - d, B - c, C - b, D - a

  4. A - b, B - d, C - c, D - a

Show answer
Correct Option: C