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Purification of Organic CompoundsPurification of organic compounds can be done by
Crystallisation Crystals obtained are in purest form of the impurity present in the
impure solid dissolves in the solvent and remains dissolved when solution is cooled.
Sublimation Conversion of solid into vapours without formation of liquid is called
sublimation.
Solid Sublimate CoolVapour Solid
Compounds to be purified must have relatively high vapour pressure and the
impurities must have vapour pressure lower than the compounds to be purified.
Distillation Liquids can be purified by distillation which is a process of vaporising
liquids and condensing the vapours as a distillate.
If liquid decomposes before boiling point, then distillation is done under reduced
pressure (when b.p. is lowered) as recovery of glycerol from spent lye.
If substance is immiscible with water steam distillation is preferred, as aniline
separated from water.
Chromatographic Method It depends on difference in the partition coefficients
(K) of the components of a mixture between two immiscible phases mobile and
stationary. The substances being separated are transported with the mobile phase.
k
C
C
s
m=
where, Csis the concentration of the substance in the stationary phase
and Cmin the mobile phase
Stationary phase(Adsorbent) Mobile phase(Eluent) Type
Solid Vapour Gas chromatography
Liquid Vapour Gas chromatography
Solid Liquid Adsorption chromatography column and TLC
Liquid Liquid Liquid-liquid Partition chromatography
Chapter
1 Purification
Elemental Analysis
Organic Compounds
andof
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Analysis of Elements(Qualitative)
Organic Compounds have carbon and hydrogen, other
elementsX(Cl, Br, I), S, N may be present
Organic compound CuO,
CO + H O2 2
CO2 turns lime water milky indicating presence of
carbon
H O2 turns anhydrous CuSO4(white) blue due to the
formation of hydrated CuSO H O.4 2 This indicatespresence of hydrogen.
Presence ofX, N, S, etc., is confirmed by Lassaignes
method, using sodium extract.
Na + C + N NaCN Na[Fe(CN) ]FeSO HCl
6123
4
N-present FeCl3
Fe[Fe(CN) ]6
Prussian blue
Na + C + N + S NaCNS NaCl
N, S bothpresent
FeCl31 24 34
+[Fe(CNS)]Cl2Red
Na + Na Yellow ppt
AgNO
AgNO
Partially soluble i
X X
3
3
nNH (Br3 2 )
White ppt AgNO3
soluble in Yellow ppt
NH3(Cl) insoluble in NH (I)3
Quantitative estimation Weight of organic
compound=wgCarbon
C CO12 g 44 g
2 C% 12 100 weight of CO2=
44 w
2H H O2 g 18 g2
H% =2 100 weight of H O2
18
Nitrogen
N NH14 17
3(neutralised by V1mL ofN1HCl)
NH N 1000 mL of 1N HCl3
N% 1.4= N V
w
1 1 (kjeldahls method)
2N N28 g 2
22400 mL
mL
V
N%=
28 100
22400
V
w (Dumas method)
Halogens
X X(Cl, Br, I) Ag
X XX w
%=
Atomic mass of weight of AgMolar mass of Ag
100
e.g., Cl 35.5 weight of AgCl 100
143.5%=
w
Molar Mass of Determination
w=weight of organic compoundW =weight of solventm=molar mass of organic compound
Cryoscopic method (based on depression in freezing
pointTf)
mK w
T W
f
f
=1000
Kf=Molal depression constant
Ebulliscopicmethod (based on elevation inboiling point)
m K w
T W
b
b
=1000
Kb=molal elevation constantSilver salt method (for organic acid)
R R w gw
COOH COOAg Ag 12
108
E w
w
(Eq. wt. of silver salt)
Eq.wt. of silver= 1
2
E w
w108
1
2
=
E w
w=108 1
2
R RCOOH COOAg Ag +H=
= +E 108 1 = E 107
Thus, equivalent weight of acid= ( )E 107
Molar mass of acid=Basicity ( )E107
Platinum salt method(for organic bases)
2B 2B 2HCl B H PtCl Pt2HCl PtCl
2 2 6 4
B H PtCl Pt2 2 6
2B + 410gw w1 2
1951 24 34 123
Molar mass of platinum salt
Atomic mass of platinum=w
w
1
2
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2 410
195
1
2
B w
w
+ =
B ww
=
12
195 4101
2
where,Bis the equivalent weight of base.
Victor Meyer Method
m wRT
pV=
where, V is the volume of vapour in litre collected at
pressurep atm and temperature. TK from w gramsolute
( )R=0.0821L atm mol K1 1
Molecular Formula Determination
Elements Percentage Mole ratior Simplest ratio
(r/smallest value ofr)
C xx
12
H yy
1
O zz
16
N ww
14
Example Molar mass of an organic compound
= 62 1g mol
C=20%H 6.67%=N 46.67%=O 26.66%=
Derive Molecular Formula
Elements Percentage % / atomic mass Ratio
C 20.00 20
12=1.66 1
H 6.676.67
6.671
= 4
O 46.6746.67 3.33
14= 2
N 26.6626.66
1.6616
= 1
Empirical formula=CH N O4 2Empirical formula weight=60
Molar mass=60 g mol1
Molar mass
Empirical formula weight= =60
601
Thus, molecular formula=(CH N O)4 2 1
=CH N O4 2
Purification andElemental Analysis ofOrganic Compounds 691
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1. Prussian blue can be represented as
Fe Fe(CN) ]6
x y
[
Oxidationnumbers of Fe atoms (indicated byxandy)are
(a) 2, 2 (b) 2, 3
(c) 3, 2 (d) 3, 3
2. In the detection of N and S both in the compound byLassaigne fusion test, blood red colour is due to theformation of
(a) [Fe(CNS)]+ (b) [Fe(CNS) ]2+
(c) [Fe(CNS) ]3 (d) [Fe(CNS)]2+
3.Sulphur is converted intoNa S2 in Lassaigne fusiontest. Na S2 can be detected by
I. CH COOH;3 II. (CH COO) Pb,3 2III. Na [Fe(CN) NO]2 5Correct codes are
(a) I, II (b) II, III
(c) I, III (d) III only
4. WhenCO2is passed into lime water, solution turns
milky due to formation of I but milkyness disappearsdue to the formation of II. I and II are
(a) CaCO ,3 Ca(HCO )3 2 (b) Ca(HCO ) ,3 2 CaCO3(c) Ca(OH) ,2 CaCO3 (d) CaCO ,3 Ca(OH)2
5. Detection of phosphorus in the compound can bedone by its conversion into phosphate. Reagent toidentify phosphate ion is(a) sodium nitroprusside
(b) ammonium molybdate
(c) potassium ferrocyanide
(d) potassium ferricyanide
6. In Carius method for the estimation of sulphur,precipitate is of
(a) BaSO4 (b) Ba(HSO )4 2(c) BaS (d) Ag S2
7. Carius method can be used for the estimation of
(a) sulphur (b) halogen(c) Both (a) and (b) (d) None of these
8. Automatic estimation of elements in organiccompound is done by
(a) ENTanalyser (b) CHNanalyser(c) MRIanalyser (d) X-rayanalyser
9. Phosphorus is estimated as
(a) Mg PO2 2 7 (b) Na PO3 4 (c) P O2 3 (d) P O2 5
10. CH NH3 2changes to CH OH3 on reaction with HNO .2There is
(a) increase in % of carbon
(b) decrease in % of carbon
(c) increase in % of hydrogen
(d) no change in % of carbon
11. Hydrocarbon X contains 3 g carbon per gram ofhydrogen. Simplest formula of the hydrocarbonXis
(a) CH (b) CH2 (c) CH3 (d) CH4
12. Which has maximum percentage of chlorine?
(a) C H Cl6 6 6 (b) CH Cl3(c) C H Cl6 5 (d) C H Cl2 4 2
13. Which is not related to C H O2 4 2in any respect?
(a) CH O2 (b) CH N O4 2(c) C H O4 4 4 (d) C H O4 8 4
14. Percentage of carbon increases when CH CH OH3 2changes to
(a) CH CHO3 (b) CH COOH3(c) CO
2 (d) In all cases
15. 10 mL of a hydrocarbon on complete combustiongave 30 mL ofCO2 and 20 mL ofH O.2 Molecularformula of the hydrocarbon is
(a) C H3 6 (b) C H3 4 (c) C H3 2 (d) C H3 3
16. 0.63 g of a dibasic acid neutralises 100 mL of 0.1 NNaOH solution. Molar mass of dibasic acid is
(a) 63 (b) 126 (c) 31.5 (d) 12.6
17. Which method is not correctly matched to determinemolecular weight?
(a) Volatile substanceVictor Meyer
(b) Organic baseplatinum salt
(c) Organic acidsilver salt(d) Non-electrolyte (like sucrose)Carius
FormatI MCQs with only Correct OptionONE
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18. Silver salt of a diabasic acid has 27% silver. Molarmass of dibasic acid is
(a) 400 (b) 200 (c) 293 (d) 586
19. Molar mass of acetic acid in benzene solventdetermined using cryoscopic method is just twice ofthe theoretical value. This is due to
(a) its ionisation into CH COO3 andH+ ions
(b) its association as dimer (CH COOH)3 2 by van derWaals forces
(c) its association as dimer (CH COOH)3 2by H-bonding
(d) that its molar mass of acetic acid is just twice oftheoretical value is not correct
20. Depression in freezing point of 1 molal urea solutionis 0.54. Depression in freezing point when 0.18 g of a
non-electrolyte is added to 10 g water is 0.054. Thus,molar mass of the non-electrolyte is
(a) 180 g mol1 (b) 90 g mol1
(c) 18 g mol1 (d) 9.0 g mol 1
21. Which of theorganic compounds will give redcolourin Lassaigne test?
(a) NaCNS (b) NH C
S
NH2 2
22. Organic compound A HNO /AgNO3 3 white ppt.
can be due to
23. In the detection of nitrogen, blue/green colour is dueto the formation of Prussian blue. It is
(a) NaFe [Fe (CN) ]III II 6 (b) NaFe [Fe (CN) ]II III 6
(c) Na [Fe(CN) ]4 6 (d) Na [Fe(CN) ]3 6
24. Which factor is most important in determining thechemistry of an organic molecule?
(a) The melting point
(b) The functional group
(c) The number of branches in the carbon chain
(d) The number of carbon-hydrogen bonds
25. 6 g of the organic compound on heating with NaOHgave NH3 which is neutralised by 200 mL of 1 NHCl. Percentage of nitrogen is
(a) 12% (b) 60%
(c) 46.67% (d) 26.67%
26. Haemoglobin is a chromoprotein having 4 atoms ofFe in each molecule. Analysis showed 0.35% Fe.Hence, its molecular weight is
(a) 64000 (b) 56000
(c) 12000 (d) 1200
27. An organic compoundAcontain 20% C, 46.66% N,6.66% H. It gaveNH3gas on heating with NaOH.Acan be
(a) CH CONH3 2 (b) C H CONH6 5 2(c) NH CONH2 2 (d) CH NHCONH3 2
28. Thesulphur content of cystine is 26.7 percent. Giventhat cystine contains two sulphur atoms, molecularweight of cystine is approximately
(a) 120 (b) 240 (c) 100 (d) 60
29. Tyrosine is one of the amino acids present in protein.Its content in protein is 0.22% and its molecular
weight is 181 g mol .1 Lowest molecular weight ofprotein is
(a) 18100 (b) 2200 (c) 82273 (d) 18132
30. Platinum salt of an organic base contains 32.5%platinum. Hence, equivalent weight of the base is(Pt=195)(a) 95 (b) 190
(c) 600 (d) 300
31. RMgBr + H O H2 R (g). Gas occupies 1.4 Lper g ofRH at STP. Hence,RMgBr is
(a) CH CH MgBr3 2 (b) C H MgBr6 5(c) CH CH CH MgBr3 2 2 (d) CH MgBr3
32. R RA B
N Cl Cl + N2 2Cu , 1 g of A gave 0.2 g ofB.
Hence,Ais
(a) CH CH N Cl3 2 2 (b) C H N Cl6 5 2(c) CH N Cl3 2 (d) None is correct
33. Glycerol can be separated from spent-lye in soapindustry by
(a) steam distillation
(b) fractional distillation
(c) distillation under reduced pressure(d) ordinary distillation
34. Aniline (an aromatic base) is separated fromwater-aniline mixture by
(a) fractional distillation
(b) steam distillation
(c) distillation under reduced pressure
(d) None of the above
35. Steam distillation is based on the fact thatvaporisation of organic liquid takes place at
(a) lower temperature than its boiling point
(b) higher temperature than its boiling point
(c) its boiling point(d) water and organic liquid both undergo distillation
Purification andElemental Analysis ofOrganic Compounds 693
(d) SO Na3HO(c) NH CNH2 2
(b) Cl
(c) Cl (d) CH3
(a) NH Cl4
Cl
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36. Naphthalene has some sand impurity. It can bepurified by
(a) sublimation
(b) steam distillation
(c) TLC
(d) column chromatography
37. Mixture of amino acids can be separated by
(a) sublimation
(b) chromatography
(c) distillation under steam
(d) distillation under reduced pressure
38. Sprayer used in the detection of amino acids is
(a) Iodine (b) Benedicts solution
(c) Fehlings solution (d) Ninhydrin solution
39. The relative adsorption of each component of themixture is expressed in terms of
(a) adsorption factor (b) retention factor
(c) co-factor (d) sorption factor
40. Adsorbent is made of in TLC.
(a) silica gel (b) alumina
(c) Both (a) and (b) (d) None of these
41. Partitioncoefficient of an organic compound( )A is20
between ether and water. 5 g of( )A in 50 mL water isshaken wih 50 mL ether. ( )A extracted into ether is
(a) 4.0 g (b) 4.2 g
(c) 4.6 g (d) 4.8 g
42. Solubility of an organic compound is 10 g/100 mLwater at 20C and 60 g/100 mL water at 70C. 30 g ofan impure organic compound is dissolved in 50 mLwater at 70C and cooled to 20C. Crystals formedweigh
(a) 5 g (b) 20 g
(c) 25 g (d) 30 g
43. The most suitable method of separation of a 1 1:
mixture ofortho-andpara-nitrophenol is
(a) sublimation (b) chromatography
(c) crystallisation (d) steam distillation
44. Which of the following techniques is most suitablefor the identification of cyclohexanone from amixture containing benzoic acid, cyclohexane andcyclohexanone?
(a) Crystallisation (b) Infra-red spectroscopy
(c) Sublimation (d) Evaporation
45. Which one of the following is not used for thepurification of solid impurities?
(a) Distillation (b) Sublimation
(c) Crystallisation (d) All of these
46. The process of distillation involves all of the
following except
(a) change of state (b) boiling(c) condensation (d) evaporation
47. Steam distillation is useful for the purification of
substances which
(a) are insoluble in water
(b) are volatile in steam
(c) are associated with non-steam volatile impurities
(d) have all the above characteristics
48. Chromatography technique is used for theseparation
of
(a) small samples of mixtures
(b) plant pigments
(c) dyestuffs
(d) All of the above
49. Which of the following is not sublimate?
(a) Naphthalene (b) Camphor
(c) Chlorine (d) Benzoic acid
50. A mixture of camphor and benzoic acid can be easily
separated by
(a) sublimation
(b) extraction with solvent
(c) fractional crystallisation
(d) chemical method
51. A compound is decomposed at its boiling point. It
can be purified by
(a) vacuum distillation (b) steam distillation
(c) fractional distillation (d) sublimation
52. Azeotropic mixtures(a) boil at different temperature
(b) are mixture of solids
(c) are constant boiling mixtures
(d) are immiscible liquids
53. Absolute alcohol cannot be obtained by simple
fractional distillation because
(a) pure C H OH2 5 is unstable
(b) C H OH2 5 forms hydrogen bonds with water
(c) boilingpoint ofC H OH2 5 is very close to that of water
(d) constant boiling azeotropic mixture is formed withwater
54. In paper chromatography(a) mobilephase is liquidandstationaryphase is solid
(b) mobilephase is solid andstationary phase is liquid(c) both phases are liquids
(d) both phases are solids
55. Mixture of benzene and chlorobenzene is separatedby
(a) sublimation (b) separating funnel
(c) crystallisation (d) distillation
56. Dumas method involves the determination ofnitrogen content in the organic coompound in theform of
(a) NH3 (b) N2(c) NaCN (d) (NH ) SO4 2 4
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57. In which of the following, molar mass determined bycrysocopic method is different from the normalvalue?
(a) Urea (b) Benzoic acid
(c) Glucose (d) Sucrose
58. Middletons fusion method uses(a) zinc
(b) sodium carbonate
(c) sodium metal
(d) mixture of zinc and sodium carbonate
59. Adsorption chromatography hasAbsorbent Eluent
(a) Solid Liquid
(b) Liquid Solid
(c) Solid Solid
(d) Liquid Liquid
60. In Dumas method of estimation of nitrogen, 0.35 g ofan organic compound gave 55 mL ofN2 collected at300 K and 715 mm pressure (aqueous tension of wateris 15mm).Percentageof nitrogenin the compound is
(a) 14.45 (b) 15.45 (c) 16.45 (d) 17.45
61. Which mixture can be separated by sublimation?
(a) Naphthalene and urea (b) Iodine and urea
(c) Both (a) & (b) (d) None of the above
62. Partition coefficient of succinic acid between ether
and water 2. 100 mL of water has 4 g succinic acid. It
is to be extracted into ether. Select the correct
statement(s).
(a) 66.66% acid is extracted if 100mL of ether is used at
one time
(b) 75.00% acid isextracted if 100mL of ether is used in
two parts of 50 mL each
(c) 80.50% acid isextracted if 100mL of ether is used in
four parts of 25 mL each
(d) All of the above are correct statements
63. A gaseous hydrocarbon gives upon combustion
0.72 g of water and 3.08 g ofCO2 . The empirical
formula of the hydrocarbon is [JEE Main 2013]
(a) C H2 4 (b) C H3 4
(c) C H6 5 (d) C H7 8
Example1 Read the following passage and answer thequestions given thereafter.
In the identification of organic compounds, preliminaryinvestigation includes detection of specific elements likenitrogen, sulphur and halogens. Research scholarAas well as
Research scholarB prepared sodium extract for the detection ofnitrogen (as they were told). In analysis there was red colour
formation for the compound of scholarAand blue colour forthe compound of scholarB.Further analysis indicated 36.84%
nitrogen in A (molar mass 76 g mol )1 and 46.67% nitrogen in B
(molar mass60 g mol )1
1. Elements in the compound analysed by A could be
(a) C, N, S (b) C, N
(c) C, N, Cl (d) C, N, O
2. Elements in the compound analysed byBcould be
(a) C, N, S (b) C, N
(c) C, N, Cl (d) C, N, Br
3. Redcolourobtained byA can bedue tothe formation of
(a) Fe(OH)3 (b) Fe(CNS)3(c) [Fe(CNS) ]2
+ (d) [Fe(CNS)]2+
4. Blue colour inBcan be due to the formation of
(a) Fe[Fe(CN) ]6 (b) Fe[Fe(CN) ]6
+
(c) Fe[Fe(CN) ]62 (d) Fe[Fe(CN) ]6
2+
Example2Thin-Layer Chromatography(TLC)
As the name implies, adsorbent is the thin layer of silica gel oralumina spread over a glass plate of suitable size and plate thus
formed as TLC plate on which solution of the mixture is placedin the form of a spot about 2 cm above one end of the TLC plate.
This treated TLC plate is placed in a closed jar having a solvent.As the solvent moves up the plate, individual componentsmove up along the plate to different distances depending on the
degree of adsorption and separation takes place.Rf,retentionfactor,which gives relative adsorption of each component in
the mixture is defined by equation.
Rf =distance moved by the spot centre from the base line
distance moved by the solvent from the base line
Readthe above passage and answer the questions at the end of it.
1. Rfvalue does not depend on
(a) type of plate (b) eluent
(c) temperature (d) pressure
2. Some of the spots in TLC analysis are colourless. Incase of amino acids colourless spots can be madevisible by(a) ninhydrin (b) sulphuric acid(c) anthraquinone (d) quinol
Purification andElemental Analysis ofOrganic Compounds 695
FormatII Comprehension Based MCQs
Base line Start
Solventfront
Start
Lid
(a)TLC beforeevelopment
(b)development of
TLC plate
(c)TLC after
development
Solvent
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3. Rfvalues ofAandBare 0.65 and 0.42 respectively.
Which of these will elute first?
(a) A (b) B(c) Equally (d) Cannot be decided
Example 3Read the following passage and answer thequestions given at the end of it.
Bonding organic compounds are generally covalent. Therefore,like inorganic compounds, no direct method is available for thedetection of elements. In sodium-fusion method covalentbonds of hetro atoms are broken by heating of organiccompounds with sodium metal. This results in the formation ofinorganic ions involving these elements; these ions can in turnbe readily identified by the inorganic qualitative methods.
1. Detection of elements in organic compound is done
using sodium-fusion method which is also called(a) Middletons fusion method
(b) Lassaigne fusion method
(c) Hofmanns method
(d) Hinsbergs method
2. Instead of sodium, one can also use following in thedetection of elements in organic compounds
(a) NaHCO3 (b) Na CO /Zn2 3(c) NaHCO / Zn3 (d) CaCO3
3. Which of theorganic compounds will give redcolourin Lassaigne test?
(a) NaCNS (b) NH C
S
NH2 2
4. In the detection of nitrogen, blue/green colour is dueto the formation of Prussian blue. It is
(a) NaFe [Fe (CN) ]III II 6 (b) NaFe [Fe (CN) ]II III
6
(c) Na [Fe(CN) ]4 6 (d) Na [Fe(CN) ]3 6
5. Red colour complex ion formed on adding FeCl3to
SE, when N and S both are present in organiccompounds is
(a) [Fe(CN) ]64 (b) [Fe(CNS)]2+
(c) [Fe(CNS) ]2+ (d) [Fe(CN) ]6
3
6. Detection of chlorine is possible without preparingsodium extract in
7. To sodium fusion extract, Cl2 water and CCl 4were
added and shaken well. There is violet colour in thelower part (organic layer). This indicates thepresence of
(a) bromine (b) iodine
(c) chlorine (d) bromine and iodine
8. Sulphur is converted into S2 on fusion with sodiumsulphide can be detected by
(a) lead acetatewhen black precipitate is formed
(b) sodiumnitroprussidewhen purple colour is formed(c) Both (a) and (b)
(d) None of the above
Example4A mixture contains the three compounds shownin the table below :
Solubility(g/100 mL)
in H O2 in ether
1. 0.31 25.0
2. 0.11 5.5
3. 3.02 106
1. Themixture is dissolvedin small amountof ether.Tothis is added an equal volume of 0.01 M HCl(aq).After shaking, two layers are formedan aqueouslayer and an ether layer. The layers are thenseparated. Which of the compounds will be found inthe aqueous layer?
(a) 1 only (b) 2 only (c) 3 only (d) 2 and 3
2. To the ether layer is added an equal volume of 0.01 MNaOH(aq). Again, two layers are formed. Afterseparating them, which of the compounds will befound in the aqueous layer?
(a) 1 only (b) 3 only
(c) 1 and 3 (d) 2 and 3
3. This aqueous layer is evaporated to dryness leaving asolid residue of mass 0.31 g. Ten millilitres ofaqueous acid of pH 3 are added. After stirring, theresidue is smaller. What is the identity of theresidue?
(a) 1 only (b) 2 only
(c) 3 only (d) 1 and 3
696 Practice Book ofChemistry forJEEMain & Advanced
(d) SO Na3H N2(c) NH CNH2 2
O
(a) CHCl3(b)
(c) CH Cl2 (d) CH2 CHCH Cl2
O N2 Cl
NO2
2
COOH
NO2
NH2
NO2
OH
NO2
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1. Match the element (in Column I) with the method(in Column II) used to determine its percentage.
Column I(Element) Column II(Method)
A. Nitrogen 1. Carius method
B. Sulphur 2. Dumas method
C. Carbon 3. Iodine method
D. Oxygen 4. Leibigs combustion method
E. Phosphorus 5. Ignition method
2. Match the compound (in Column I) with the reagentused to test them (in Column II).
Column I(Compound) Column II(Reagent)A. Na S2 1. HNO /AgNO3 3B. Na [Fe(CN) ]3 6 2. FeCl3C. NaCNS 3. (CH COO) Pb3 2D. NaI 4. FeCl2
3. Match the organic substance (in Column I) with themethod of determination of its molar mass(in Column II).
Column I(Substance) Column II(Method)
A. An organic acid 1. Platinum-salt method
B. A base 2. Victor-Meyer method
C. Non-electrolyte 3. Silver-salt method
D. A volatile substance 4. Cryoscopic method
4. Match the compound in Column I with the compondobtained with sodium fusion test in Column II.
Column I(Compound)
Column II(Compound
obtained withsodium fusion test)
A. 1. [Fe(CNS)]2+
B. 2. [Fe(CN) NO]52
C. NH C
O
NH2 2
3. Fe [Fe (CN) ]
III II6
D. 4. [Ag(NH ) ]3 2+
5. Match the compounds in Column I with theircharacteristic test(s)/reaction(s) given in Column II.
Column I(Compound) Column II(Tests)
A. H NNH Cl2 3
1. Sodium-fusionextract of thecompound givesPrussian blue colourwith FeSO4
B. 2. Gives positive FeCl3test
C.3. Gives white
precipitate withAgNO3
D. 4. Reacts withaldehydes to formthe correspondinghydrazone derivative
6. Match the compound in Column I with thecharacteristic tests in Column II.
Column I(Compound) Column II(Characteristictests)
A. 1. Gives whiteprecipitate withAgNO3( )aq
B. 2. Gives positive FeCl3test
C.
3. Sodium fusionextract of thecompound givesPrussian blue colourwith FeCl3
D. 4. Gives red colourwith cericammonium nitrate
Purification andElemental Analysis ofOrganic Compounds 697
H C3 SO NH2 2
ClH C2 SO H3
Cl
O N2
HONH I3
COOH
HO NH Cl3
O N2 NHNH Br3
NO2
O N2 Cl
NO2
NO2
HOH C2 CH Cl2
OH
Cl CNH2
CH OH2
O
H N2 OH
CH CH Cl2 2
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1. Total number of atoms in empirical formula of aceticacid is .
2. When one mole of acetone is completely combustedratio ofCO2and H O2 formed is
3. An organic compound weighing 0.203 g gave oncombustion 0.378 g ofCO2and 0.128 g ofH O.2 Thus,percentage of hydrogen is .
4. Magnitude of chargeon Prussian blueFe[Fe(CN) ]6 is
5. An organic compound weighing x g containing46.67% nitrogen on heating with NaOH gave NH3which is neutralised by200 mL of 1 N HCl. Thus,xis
6. Deep violet colour formed when sodium extract ofthe organic compound containing sulphur is treated
with sodium nitroprusside has structure
Na [Fe(CN) NOS]2 x wherexis
7. Acetic acid is converted into silver salt and 4.64 g of
the silver salt on decomposition gave silver g.
8. Haemoglobin (molecular weight 64000) is a
chromoprotein having x atoms of Fe in each
molecule. Analysis showed 0.35% Fe. Thus,xis .
1. (c) Fe[Fe(CN) ]6
Prussian blue is formed when Fe3+ salts react with
[Fe (CN) ]II 64
Fe [Fe(CN) Fe [Fe (CN) ]III II 63
64+ + ]
Thus, x= 3y= 2
2. (d) Sodium extract has= NaCNS
FeCl + NaCNS [Fe(CNS)]Cl + NaCl3 2
3. (b) Na S + ( CH COO) Pb PbS + 2 CH COONa2 3 2 3black
Na S+ Na [Fe(CN) NO] Na [Fe(CN) NOS]2 2 5 4 5violet-purple
4. (a) Ca(OH) + CO CaCO + H O2 2 3 2milky (I)
CaCO + H O + CO Ca(HCO )3 2 2 3 2
soluble (II)
5. (b) Na PO + 12(NH ) MoO + 21HNO3 4 4 2 4 3
(NH ) PO 12MoO 21NH NO + 3NaNO + 1 2H O4 3 4 3 4 3 3 2yellow ppt
+
6. (a) S H SO BaSOHNO BaCl3
2 4 4 2
7. (c) 8. (b)
9. (a) PO Mg (PO ) Mg P OMg
3 4 2 2 2 743
10. (b) CH NH3 2 CH OH3
Molar mass= 31 Molar mass= 32= 38.71% C% = 37.5%
11. (d) Total amount= + =3 1 4 g
moles ratio
% of C = 75% 6.25 1
% of H = 25% 25.0 4
Thus, formula is CH4.
12. (a) (a) C H Cl (CHCl)6 6 6 6 Cl 35.548.5
%= 100
(b) CH Cl3 Cl 31.5
50.5%=
100
(c) C H Cl6 5 Cl 35.5
112.5%=
100
(d) C H Cl (CH Cl)2 4 2 2 2 Cl 35.5
49.5%=
100
ClDenominator (which is minimum in (a))
% 1
13. (c) (a) CH O C H O2 2 4 2
(b) CH N O,4 2
molar mass (60)
C H O ,2 4 2 molar mass (60)
(c) C H O4 4 2is not related to molar mass and also not to
formula
(d) C H O (C H O )4 8 4 2 4 2 2
14. (a) (a) CH CH OH = 52.173 224 100
46
=
(b) CH CHO 54.543 = =24 100
44(increases)
(c) CH COOH = 24 100
3
=60
40%
(d) CO 27.17%212 100
44
24 100
88= = =
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15. (b) C H4
O CO2
H O
1 mL2
2 2 2x y x y
x y
x y
+ +
+
10 30x= ,10
220
y =
x= 3,y= 4
16. (b) Equivalent of dibasic acid =equivalent of NaOH0.63 0.1
E= 100
1000
E= 63 Molar mass = 63 2 = 126 g mol1
17. (d)
18. (d)Equivalent weight of silver salt
Equivalent weight of silver=
Weight of silver salt
Weight of silver
E
108
100
27=
E= 400Equivalent weight of acid= 400 107= 283
Molar mass= =283 2 586
19. (c) CH C
O - - - H O
O H - - - O
CCH3 3
20. (a) T Kf f= molality
0.54 = 1 Kf Kf=
0.54 molal 1
Also T K wm W
ff= 100 (solute)
(solute) (solvent)
0.054 0.54 0.18=
1000
10m
m= 180 g mol 1
21. (b) If NaCNS is formed in sodium extract then red colour is
formed.
NaCNS + FeCl [Fe(CNS)] Cl + N aCl3 2red
(a) Inorganic salt
Cl + Ag AgCl +
white ppt.
(a) Also gives white ppt. but it is inorganic salt.
23. (a) Prussian blue colour is formed.
Na [ Fe(CN) ]+ F eCl 3NaCl + NaFe [Fe (CN) ]4 6 3III II
6
24. (b)
25. (c) Percentage of N 1.4
(compound)= NV
w
= 1.4 1 200
6
=46.67%26. (a) When 0.35 g Fe = molar mass is 100
4 56 g Fe =100 4 56
0.35
=64000
27. (c) % Moles Ratio Empirical formula
C 20 1.66 1
CH N O4 2H 6.66 6.66 4
N 46.66 3.33 2
O 26.67 1.66 1
A NaOH/ NH 3,thus (CONH2 )group hence A isNH CONH2 2
28. (b) Let molar mass of compound= 100
Sulphur atom= 26.7%When 26.7 g sulphur, molar mass = 100 1g mol
When 64 g sulphur, molar mass = 100 6426.7
= 239.7
29. (c) When molar mass is 100then proteincontent is 0.22%
Molar mass of protein=
100
1810.22
=8227330. (a) Platinum salt of a base is H B PtCl2 2 6
2 + H PtCl H B PtCl Pt2 6 2 2 6(410 + 2 ) 195
BB
(2 + 410) molar mass of platinum salt
(195) molar
B
mass of platinum
100
32.5=
B=9531. (d) H O2 decomposesRMgBr formingRH
1.4 L ofRH at STP = 1 g
22.4 L ofRH at STP
22.4
1.4= 16 g
=Thus,RH is CH4.
Hence,RMgBr is CH MgBr3 .
32. (b) R RR
N Cl CN + N2 2( 28 35.5) Cu 28 g+ +
R+ =63.5 10.228
R= 76.5 77RN Cl2 is C H N Cl6 5 2
33. (c) 34. (b) 35. (a) 36. (a) 37. (b)
38. (d) 39. (b) 40. (c)
41. (d) LetAextracted into ether= xg
Purification andElemental Analysis ofOrganic Compounds 699
Cl + Cl
Allylic carbocation
(resonance stabilised)
( )b22.
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Aleft in water= ( )5 x g
conc. ofAin water=
5
50
x
conc. ofAin ether= x50
Given, C
C
x
x
x
xA
A
(ether)
(water)= = =
20 505
50
5
x= 4.8 g
42. (c) Organiccompound solution hasbeen cooled to 20C.
100 mL H O2 can dissolve= 10 g50 mL H O2 can dissolve= 5 g
Solute taken= 30 g
Hence, solute crystallised= 25 g43. (d) 44. (b) 45. (a) 46. (a) 47. (d)
48. (d) 49. (c) 50. (d) 51. (a) 52. (c)
53. (d) 54. (a)
55. (d) They differ in boiling point.
56. (b)
57. (b) Dimer is formed due to intermolecular H-bonding.
Molar mass is twice the normal value.
58. (d) 59. (a)
60. (c) RNH HNO N + H O
g 22400 mL at NTP
2 22 2
28
123
+
Actual pressure= =715 15 700 mmp V
T
p V
T1 1
1
2 2
2
=
STP given
V T p V
T p1
1 2 2
2 1
= =
273 700 55
300 760=46.09mL
Thus, N
46.09
0.35%=
28 100
22400 = 16.45
61. (c) 62. (d) 63. (d)
Ex.1 1.(a) 2. (b) 3. (d) 4. (a)
Ex.2 1.(d) 2. (a) 3. (b)
Ex.3 1.(b) 2. (b) 3. (b,d) 4. (a) 5. (b)
6.(a,c,d) 7. (b) 8. (c)
Ex.4 1.(b) 2. (b) 3. (b)
1. A(2); B(1); C(4); D(3); (E)5
2. A(3); B(4); C(2); D(1);
3. A(3); B(1); C(4); D(2)
4. A(1,3); B(1,2); C(3,4); D(1,2,3)
5. A(3,4); B(1,2); C(1,2,3); D(1,4)
6. A(1); B(2,4); C(3); D(3,4)
Questions 1 2 3 4 5 6 7 8Answers 4 1 7 1 6 5 3 4
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