Purification and Characterisation of Organic Compounds — DPP 1

20 NEET questions from Purification and Characterisation of Organic Compounds, with answers and explanations. Attempt it as a timed test to get scoring, accuracy breakdown and mistake tracking.

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1
Ether and benzene can be separated by :-
  1. A Filtration
  2. B Distillation
  3. C Crystallization
  4. D Sublimation
Show answer & explanation

Correct answer: B

B.P. of Benzene = 353 K
B.P. of Ether = 308 K
Difference of B.P. = 353 – 308 = 45 K
Since the difference in B.P. is greater than 40,
these can be separated by simple distillation.
2
The purification method where solid substance change from vapour state without passing through the liquid state is called as
  1. A Sublimation
  2. B Crystallization
  3. C Distillation
  4. D Differential extraction
Show answer & explanation

Correct answer: A

The process of conversion of sublimable solid to vapour state directly by heating without passing through liquid state is called sublimation.
3
The formula of the purple/violet colour formed in Lassaigne's test for sulphur using sodium nitroprusside is
  1. A $\mathrm { NaFe } \left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 6 } \right]$
  2. B $\mathrm { Na } \left[ \mathrm { Cr } \left( \mathrm { NH } _ { 3 } \right) _ { 2 } ( \mathrm { NCS } ) _ { 4 } \right]$
  3. C $\mathrm { Na } _ { 2 } \left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 5 } ( \mathrm { NO } ) \right]$
  4. D $\mathrm { Na } _ { 4 } \left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 5 } ( \mathrm { NOS } ) \right]$
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Correct answer: D

Sodium fusion extract is treated with freshly prepared sodium nitroprusside, appearance of violet colour (purple) indicates presence of sulphur.
4
Statement-I :- Crystallisation is one of the most commonly used techniques for the purification of liquid organic compounds.
Statement-II :- Crystallisation is based on the difference in the solubilites of the compound and the impurities in a suitable solvent.
  1. A Both Statement I and Statement II are true.
  2. B Both Statement I and Statement II are false.
  3. C Statement I is true but Statement II is false.
  4. D Statement I is false but Statement II is true.
Show answer

Correct answer: D

5
R$_{f}$ value (Retardation factor)
(i) Distance moved by substance from base line (a)
(ii) Distance moved by solvent from base line (b)
  1. A $\frac{a}{b}$
  2. B $\frac{b}{a}$
  3. C Both
  4. D None
Show answer

Correct answer: A

6
The substance which can be commonly used as an adsorbent in column chromatography is
  1. A Na$_ { 2 }$O
  2. B NaCl
  3. C Al$_ { 2 }$O$_ { 3 }$
  4. D Alum
Show answer & explanation

Correct answer: C

The most commonly used adsorbent in column chromatography is Al2O3 and silica gel because there have high surface area and porous in nature such that they absorb substance on to the surface by intermolecular forces.
7
Match the column :-
Purification and Characterisation of Organic Compounds – NEET-11919
  1. A a = r, b = p, c = r, d = s
  2. B a = q, b = p, c = r, d = s
  3. C a = p, b = s, c = r, d = q
  4. D a = r, b = s, c = p, d = q
Show answer & explanation

Correct answer: C

(a) Kjeldahl’s method → (p) NH₃
(b) Carius method → (s) AgCl
(c) Dumas method → (r) N₂
(d) Lassaigne’s Test→ (q) NaCN
8
Match the column :-
Purification and Characterisation of Organic Compounds – NEET-11896
  1. A a = q, b = s, c = r, d = p
  2. B a = p, b = q, c = r, d = s
  3. C a = q, b = r, c = s, d = p
  4. D a = r, b = q, c = s, d = p
Show answer & explanation

Correct answer: D

(a) [Fe(CN)$_{5}$NOS]$^{4–}$ → (r) Violet
(b) [Fe(SCN)]$^{2+}$ → (q) Blood red
(c) (NH₄)$_{3}$PO$_{4}$.12MoO$_{3}$ → (s) yellow
(d) Fe$_{4}$[Fe(CN)$_{6}$]$_{3}$.xH$_{2}$O → (p) Prussian blue
9
Chloroform (B.P. 334 K) and aniline (B.P. 457 K) are easily separated by the technique of
  1. A Crystallisation
  2. B Distillation
  3. C Sublimation
  4. D Chromatography
Show answer & explanation

Correct answer: B

Mixture of chloroform and aniline can be separated by simple distillation as there two liquids have sufficient difference in boiling point.
10
Match List I with List II:
Purification and Characterisation of Organic Compounds – NEET-11926
  1. A A-IV, B-I, C-III, D-II
  2. B A-III, B-IV, C-I, D-II
  3. C A-II, B-I, C-III, D-IV
  4. D A-III, B-I, C-IV, D-II
Show answer

Correct answer: B

11
Phenol on reaction with dilute nitric acid, gives two products. Which method will be most effective for large scale separation
  1. A Chromatographic separation
  2. B Fractional crystallisation
  3. C Steam distillation
  4. D Sublimation
Show answer & explanation

Correct answer: C

Steam distillation is used for separation and purification of organic compounds which are steam volatile and are insoluble in water.
Purification and Characterisation of Organic Compounds – NEET-11885
12
Match the column :-
Purification and Characterisation of Organic Compounds – NEET-11917
  1. A a = q, b = s, c = p, d = r
  2. B a = s, b = q, c = p, d = r
  3. C a = r, b = p, c = q, d = s
  4. D a = s, b = p, c = q, d = r
Show answer & explanation

Correct answer: B

(a) For N present in compound → (s) Na fusion extract gives blue colour
(b) For N & S present in compound → (q) Na fusion extract gives blood red colour
(c) For P present in compound → (p) Oxidised product gives yellow PPT with HNO₃ followed by (NH₄)$_{2}$ MoO$_{4}$
(d) For s present in compound → (r) Na fusion extract gives black ppt with (CH$_{3}$COO)$_{2}$ Pb.
13
For which of the following compounds Kjeldahl method is not used for estimation of nitrogen ?
Purification and Characterisation of Organic Compounds – NEET-11895
  1. A A, B, D and E
  2. B A, B and D
  3. C A and D
  4. D D and E
Show answer & explanation

Correct answer: B

Kjeldahl method is not applicable to compounds containing nitrogen in nitro and azo groups and nitrogen present in the ring (eg. Pyridine) as nitrogen of these compounds does not change to ammonium sulphate under these conditions.
14
Statement-I : Silica gel and alumina are used as adsorbent for adsorption chromatography.
Statement-II : Paper chromatography is a type of partition chromatography.
In the light of above statements, select the correct option.
  1. A Statement-I is true but statement-II is false
  2. B Statement-I is false but statement-II is true
  3. C Both statements-I and II are true
  4. D Both statements-I and II are false
Show answer & explanation

Correct answer: C

Both statement I and II are true.
15
Match items of column I and II
Purification and Characterisation of Organic Compounds – NEET-11925 Correct match is :
  1. A A-(iii), B-(iv), C-(ii), D-(i)
  2. B A-(i), B-(iii), C-(ii), D-(iv)
  3. C A-(ii), B-(iii), C-(iv), D-(i)
  4. D A-(ii), B-(iv), C-(i), D-(iii)
Show answer

Correct answer: C

16
Match the column :-
Purification and Characterisation of Organic Compounds – NEET-11894
  1. A a = q, b = p, c = r, d = s
  2. B a = p, b = q, c = s, d = r
  3. C a = q, b = p, c = s, d = r
  4. D a = p, b = q, c = r, d = s
Show answer & explanation

Correct answer: C

(a) Liquids having sufficient difference in boiling point → (q) Distillation
(b) Difference of boiling points of liquids is not much. → (p) Fractional distillation
(c) Compounds which decompose at or below their boiling point → (s) Distillation under reduced pressure
(d) Substances which are steam volatile and are immiscible with water → (r) Steam distillation
17
In Lassaigne extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with $\mathrm { Fe } ^ { 3 + }$, due to formation of
  1. A NaSCN
  2. B $\left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 5 } \mathrm { NOS } \right] ^ { 4 - }$
  3. C $[ \mathrm { Fe } ( \mathrm { SCN } ) ] ^ { 2 + }$
  4. D $\mathrm { Fe } _ { 4 } \left[ \mathrm { Fe } ( \mathrm { CN } ) _ { 6 } \right] 3 - \mathrm { x } \mathrm { H } _ { 2 } \mathrm { O }$
Show answer & explanation

Correct answer: C

When both nitrogen and sulphur are present in an organic compound sodium thiocyanate is formed, which gives blood red colour with Fe$^{+3}$
Na + C + N + S → NaCNS
Fe$^{+3}$ + SCN¯ → [Fe(SCN)]$^{+2}$ (blood red)
18
In carius method of estimation of halogen, 0.15 g of an organic compound gave 0.12 g of AgBr. Find out the percentage of bromine in the compound.
  1. A $40 \%$
  2. B $34.04 \%$
  3. C $43.04 \%$
  4. D $53.04 \%$
Show answer & explanation

Correct answer: B

Mass of bromine = 80 u
Mass of Ag Br = 188 u
Weight of Ag Br = 0.12 g
Weight of organic compounds = 0.15 g
Percentage of Bromine
= $\frac{\text { Molar mass of bro mine × weight of } \mathrm{Ag} \mathrm{Br}}{\text { Molar mass of } \mathrm{Ag} \mathrm{Br} \times \text { weight of O.C. }}$
= $\frac{80 \times 0.12}{188 \times 0.15} \times 100$
Percentage of bromine = 34.04%
19
Given below are two statements :
Statement I : In 'Lassaigne's Test, when both nitrogen and sulphur are present in an organic compound, sodium thiocyanate is formed.
Statement II : If both nitrogen and sulphur are present in an organic compound, then the excess of sodium used in sodium fusion will decompose the sodium thiocyanate formed to give NaCN and Na$_{2}$S.
In the light of the above statements, choose the most appropriate answer from the options given below :
  1. A Both Statement I and Statement II are correct.
  2. B Both Statement I and Statement II are incorrect.
  3. C Statement I is correct but Statement II is incorrect.
  4. D Statement I is incorrect but Statement II is correct.
Show answer

Correct answer: A

20
Correct match :-
Purification and Characterisation of Organic Compounds – NEET-11886
  1. A A-P, B-Q, C-R, D-S
  2. B A-P, B-S, C-R, D-Q
  3. C A-P, B-R, C-S, D-Q
  4. D A-R, B-S, C-P, D-Q
Show answer & explanation

Correct answer: B

Chloroform and aniline = Distillation
Glycerol and spentlye = Distillation under Reduced pressure
Aniline and water = steam distillation
Amino acid = chromatography

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