Tag: chemistry

Questions Related to chemistry

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

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  1. condense in upper most portion'

  2. condense in lower most portion

  3. condense in middle portion

  4. none of these

Show answer
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?

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  1. Distillation under reduced pressure

  2. Distillation

  3. Steam distillation

  4. Sublimation

Show answer
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

Show answer
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

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  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?

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  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.

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  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?

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  1. Electrolysis

  2. Distillation in a flask or a big tower

  3. Filtration through a filtering medium

  4. Leaching

Show answer
Correct Option: A
Explanation:

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

Refining of petroleum does not involve.

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  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

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  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

Carbon monoxide is naturally produced by oxidation of   X  , a gas present in swamp area while it can be produced by   Y     of fuels containing carbon.

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  1. X - $CO _{2}$, Y = complete combustion

  2. X - $CH _{4}$, Y = incomplete combustion

  3. X = C, Y = oxidation

  4. X = $CH _{4}$, Y = complete combustion

Show answer
Correct Option: B
Explanation:

Carbon monoxide is basically formed when an object is burned. Methane, which is a natural gas produces  CO after oxidation. Methane, produces less CO as compared to other units of gas. Incomplete combusion results in creation of poisonous CO. It occurs when supply of oxygen is poor.