Tag: organic chemistry : some basic principles and techniques

Quizzes (5) Questions (47)

Questions Related to organic chemistry : some basic principles and techniques

Multiple choice 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

Which one of the following reagent is useful for separating aniline from nitrobenzene?

  1. $ aq. NaHCO _3 $
  2. $ aq. NaHSO _3 $
  3. $ aq. HCl $
  4. $dil. H _2SO _4 $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The reagent selected should be such that only one of components to be separated, reacts with it.


Aniline $+$ aq, HCl $\rightarrow$ salt, which is soluble in water
Nitrobenzene $+$ aq. HCl$\rightarrow$ no reaction.

Therefore, aq. HCL is used to separate aniline and nitrobenzene.

Multiple choice 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

 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:

  1. 80%

  2. 40%

  3. 28%

  4. 60%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using Dalton's law for steam distillation: P_total = P_water + P_chlorobenzene. 740.2 = 530 + P_chlorobenzene, so P_chlorobenzene = 210.2 torr. The mole ratio n_c/n_w = P_c/P_w = 210.2/530 = 0.396. Mole fraction of chlorobenzene = 0.396 / (1 + 0.396) = 0.283, or 28%.

Multiple choice 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

Mixed melting point is determined to check.

  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
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Multiple choice 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

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

  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)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sublimation is used for benzoic acid and benzaldehyde (iii). Distillation is for ether and toluene (i). Vacuum distillation is for glycerol (iv). Steam distillation is for o-nitrophenol and p-nitrophenol (ii).

Multiple choice 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

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


  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)
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice 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

Which method cannot be used for purification
of liquids?

  1. Chromatographic

  2. Steam distillation

  3. Sublimation

  4. Distillation
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

Multiple choice 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

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.

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice 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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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. 

Multiple choice 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

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

  1. salt formation

  2. fractional distillation

  3. fractional crystallisation

  4. chromatography
Reveal answer Fill a bubble to check yourself
A Correct answer
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.