Chemistry · Science General

Separation Techniques

813 Questions

Separation techniques involve physical methods to isolate mixtures, including distillation, filtration, and crystallization. Competitive exams frequently test these foundational concepts. Review the exact processes to enhance problem solving speed.

Distillation and evaporationCrystallization processFiltration methodsSeparating dissolved solidsChromatography and mass techniques

Separation Techniques Questions

Multiple choice distinction between pairs of amines organic compounds containing nitrogen organic compounds with functional group containing nitrogen chemistry

Primary, secondary, tertiary amines can be separated by the following except: 

  1. Fractional distillation

  2. Fractional method using diethyl oxalate
  3. Hinsberg's method using $\displaystyle { C } _{ 6 }{ H } _{ 5 }{ SO } _{ 2 }Cl$

  4. Selective crystallisation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Separation of $1^o,\, 2^o$ and $3^o$ amines:

$1^o,\, 2^o$ and $3^o$ amines + $R _4NX \xrightarrow{distillation}$ Mixture of $1^o,\, 2^o,\, 3^o$ amine
Mixture  of $1^o,\, 2^o,\, 3^o$ amine can be separated by following methods.
(i) Fractional distillation: The mixture of amines may be fractional distillation because their boiling points are quite different. It is used in industry.

(ii) Hinsberg method: In this method mixture of amines is seperated by using benzene sulphonyl chloride (Hinsberg's reagent).
$C _6H _5SO _2Cl+1^o\,amine \to Product \xrightarrow{KOH} dissolve$
$C _6H _5SO _2Cl+2^o\,amine \to Product \xrightarrow{KOH} insoluble$
$3^o$ amine does not react with benzene sulphonyl chloride.

(iii) Hofman method: In this method mixture of amines is separated by using ethyl oxalate.
$1^o$ amine + ethyl oxalate $\to$ solid product
$2^o$ amine + ethyl oxalate $\to$ liquid product
$3^o$ amine + ethyl oxalate $\to$ No reaction

Multiple choice distinction between pairs of amines organic compounds containing nitrogen organic compounds with functional group containing nitrogen chemistry

Mixture of $1^0, 2^0 $ and $3^0$ amines can be separated by :

  1. Hinsberg's method

  2. Hofmann's isocyanide test

  3. Fractional distillation
  4. $NaNO _2/ HCl$
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation
All the given methods can be used for the separation of amines.

(A) Hinsberg reaction is a chemical test for the detection of amines. A primary amine will form a soluble sulfonamide salt which precipitates after addition of diluted hydrochloric acid. A secondary amine in the same reaction will directly form an insoluble sulfonamide. A tertiary amine will not react with the sulfonamide but is insoluble. After adding dilute acid this insoluble amine is converted to a soluble ammonium salt. 

(B) In Hofmann's isocyanide test the mixture of three amines is treated with diethyl oxalate. The primary amine forms a solid oxamide, a secondary amine gives a liquid oxamic ester while tertiary amine does not react.

(C) In fractional distillation primary amine is recovered when solid oxamide is heated with caustic potash solution and collected as distillate on distilling the reaction mixture. The liquid is subjected to fractional distillation when tertiary amine distils over. The remaining liquid is distilled with KOH to recover secondary amine.

(D) Nitrosation of Amines can also be used for separation as primary amine with $NaNO _2 + HCl$ forms $RN _2$, secondary amine forms $R _2N _2O$ and tertiary amine forms $R _3NO$ which decomposes into $NR _3$.
Multiple choice distinction between pairs of amines organic compounds containing nitrogen organic compounds with functional group containing nitrogen chemistry

Primary, secondary and tertiary amines may be separated by using:

  1. iodoform

  2. diethyloxalate

  3. benzenesulphonyl chloride

  4. acetyl chloride
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The amine is treated with benzenesulphonyl chloride  and shaken with alkali solution when the three amine because in different way$.$

Primary amine from alkyl benzesulphoramide which dissolve in alkali to from sodium potassium salt of mono alkyl benzene sulphoramide$.$ Secondary amine from dialkali benzene$,$ in soluble in alkali solution and tertiary amines do not react with benzene sulphonyl chloride at all$.$

Multiple choice chemistry measurement and data processing and analysis spectroscopic identification of organic compounds materials science introduction superconducting metals and x-ray crystallography

What is Analytical chemistry?

  1. The study of the separation, identification, and quantification of the chemical components of natural and artificial materials.

  2. The study of the chemical composition and structure of substances.

  3. The study of the only separation of the chemical components of natural and artificial materials.

  4. The study of the only identification of the chemical components of natural and artificial materials.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Analytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials.

Hence, 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

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

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

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

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.

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

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

  1. organic compound is highly soluble

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

  4. compound is insoluble
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  1. condense in upper most portion'

  2. condense in lower most portion

  3. condense in middle portion

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

  1. Distillation under reduced pressure

  2. Distillation

  3. Steam distillation

  4. Sublimation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

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

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 of following is incorrectly matched?

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All the listed statements are correct: simple distillation is for stable liquids, reduced pressure for heat-sensitive liquids, and steam distillation for immiscible liquids.