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Questions Related to chemistry

 A mixture of two immiscible liquids chlorobenzene and water boils at $90^{0}C$ and an external pressure of 740.2 torr. If vapour pressure of pure water at $90^{0}C$ is 530 torr then the mole % of chlorobenzene in the distillate will be:

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. 80%

  2. 40%

  3. 28%

  4. 60%

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Correct Option: C

Mixed melting point is determined to check.

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. The purity of organic compound

  2. Whether the two compounds are same

  3. Whether the two compounds are different

  4. Whether the two compounds can be separated by fractional crystallisation method

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Correct Option: A,B,C

Match the following:

(A) Sublimation (i) Ether $+$ toluene
(B) Distillation (ii) o-Nitrophenol $+$ p-nitrophenol
(C) Vacuum distillation (iii) Benzoic acid $+$ benzaldehyde
(D) Steam distillation (iv) Glycerol from spent lye
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)-(iv), (B)-(iii), (C)-(ii), (D)-(i)

  2. (A)-(i), (B)-(ii), (C)-(iii), (D)-(iv)

  3. (A)-(iii), (B)-(i), (C)-(iv), (D)-(ii)

  4. (A)-(ii), (B)-(iv), (C)-(i), (D)-(iii)

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Correct Option: C

Compare List I and List II and choose the correct matching codes from the choices given.


List I List II
(A) Glycerol (i) Sublimation
(B) o-nitrophenol (ii) Beilstein's test
(C) Anthracene (iii) Victor-Meyer's method
(D) Halogens (iv) Steam distillation
(E) Molecular weight (v) Vacuum distillation
(vi) Eudiometry


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-v), (B-iv), (C-i), (D-ii), (E-iii)

  2. (A-iv), (B-v), (C-i), (D-vi), (E-ii)

  3. (A-vi), (B-iv), (C-i), (D-iii), (E-ii)

  4. (A-v), (B-iv), (C-vi), (D-ii), (E-iii)

  5. (A-iv), (B-vi), (C-ii), (D-iii), (E-v)

Show answer
Correct Option: A
Explanation:
  • Sublimation-Conversion of solid directly into gaseous phase. The liquid state does not exist. e.g., naphthalene, anthracene. 
  • Beilstein test-Simple chemical test for halogens. 
  • Victor-Meyers method-Standard laboratory method for determining the molecular weight of a volatile liquid. 
  • Steam distillation- Vaporization of the volatile constituents of a liquid. It is special type of distillation for temperature-sensitive materials like aromatic natural compounds, eg,-ortho nitrophenol, cinnamaldehyde. 
  • Vacuum distillation-Distillation at reduced pressure. It is generally used in case of high boiling liquids which decompose below their normal boiling points, cant be purified by distillation at atmospheric pressure.
  • Eudiometry-It is the process of determining the constituents of a gaseous mixture by eudiometer. It is used for ascertaining the purity of air or amount of $O _2$ in it.

Mixture of benzene and aniline can be separated by?

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

  2. Steam distillation

  3. dil. HCl

  4. di. NaOH

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Correct Option: A,C

Which method cannot be used for purification
of liquids?

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. Chromatographic

  2. Steam distillation

  3. Sublimation

  4. Distillation

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Correct Option: C
Explanation:

Sublimation is the process in which solid changes directly to vapour state without passing through the liquid state.So sublimation cannot be used for purification of liquids.

Choose the correct option for the two statements given below :
Statement I: Sharp melting point can be used to test the purity of the compound.
Statement II: Impurities cause a decrease in the melting point of the compound.

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. Both statements I and II are correct.

  2. Both statements I and II are incorrect.

  3. Statement I is correct and statement II is incorrect.

  4. Statement I is incorrect and statement II is correct.

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Correct Option: A
Explanation:

The purity of an organic compound can be tested by its sharp melting point. The impurities present in the compound can cause a decrease in melting point.


The presence of even a small amount of impurity will lower a compound's melting point by a few degrees and broaden the melting point temperature range.

Option A is correct.

Assertion (A): Components of rectified spirit
cannot be separated by distillation
Reason (R): Rectified spirit is an Azeotropic
mixture

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. Both A and R are true and R is correct explanation of A

  2. Both A and R are true and R is not correct explanation of A

  3. A is true but R is false

  4. A is false but R is true

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Correct Option: A
Explanation:

An azeotropic is a mixture of 2 or more liquids in such a way that its components cannot be altered by simple distillation, This happens because when an azeotrope is barred, the vapour has the same proportions of constituents as the unboiled mixture.
Azeotropes are also called constant boiling mixture,
Rectified spirit is an azeotropic mixture of ethanol and water. 

d- tartaric acid and l - tartaric acid can be separated by:

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. salt formation

  2. fractional distillation

  3. fractional crystallisation

  4. chromatography

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Correct Option: A
Explanation:

d- tartaric acid and l - tartaric acid can be
separated by Salt formation.
Two enantiomers of sodium ammonium salt of tartaric acid give rise to two distinctly different types of chiral crystals that can be easily separated.

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

Show answer
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.