MaterialdownloadedfrommyCBSEguide.com. 1/43

CBSEClass–12SubjectChemistry

NCERTSolutions

Chapter–09

CoordinationCompounds

In-textquestion

1.Writetheformulasforthefollowingcoordinationcompounds:

(i)Tetraamminediaquacobalt(III)chloride

(ii)Potassiumtetracyanonickelate(II)

(iii)Tris(ethane-1,2-diamine)chromium(III)chloride

(iv)Amminebromidochloridonitrito-N-platinate(II)

(v)Dichloridobis(ethane-1,2-diamine)platinum(IV)nitrate

(vi)Iron(III)hexacyanoferrate(II)

Ans.(i)

(ii)

(iii)

(vi)

(v)

(vi)

2.WritetheIUPACnamesofthefollowingcoordinationcompounds:

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 2/43

(i)

(ii)

(iii)

(iv)

(v)

(vi)

Ans.(i)Hexaamminecobalt(III)chloride

(ii)Pentaamminechloridocobalt(III)chloride

(iii)Potassiumhexacyanoferrate(III)

(iv)Potassiumtrioxalatoferrate(III)

(v)Potassiumtetrachloridopalladate(II)

(vi)Diamminechlorido(methanamine)platinum(II)chloride

3.Indicatethetypesofisomerismexhibitedbythefollowingcomplexesanddrawthe

structuresfortheseisomers:

(i)

(ii)

(iii)

(iv)

Ans.(i)Bothgeometrical(cis-,trans-)isomersfor canexist.Also,

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 3/43

opticalisomersforcis-isomerexist.

Trans-isomerisopticallyinactive.Ontheotherhand,cis-isomerisopticallyactive.

(ii)Twoopticalisomersfor exist.

Twoopticalisomersarepossibleforthisstructure.

(iii)

Apairofopticalisomers:

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 4/43

Itcanalsoshowlinkageisomerism.

and

Itcanalsoshowionizationisomerism.

(iv)Geometrical(cis-,trans-)isomersof canexist.

4. Give evidence that and are ionization

isomers.

Ans.Whenionizationisomersaredissolvedinwater,theyionizetogivedifferentions.These

ionsthenreactdifferentlywithdifferentreagentstogivedifferentproducts.

5. Explain on the basis of valence bond theory that ion with square

planar structure is diamagnetic and the ion with tetrahedral geometry is

paramagnetic.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 5/43

Ans.Niisinthe+2oxidationstatei.e.,in configuration.

There are 4 ions. Thus, it can either have a tetrahedral geometry or square planar

geometry. Since ion is a strong field ligand, it causes the pairing of unpaired 3d

electrons.

It now undergoes hybridization. Since all electrons are paired, it forms diamagnetic

compound.

Incaseof ,Cl-ionisaweakfieldligand.Therefore,itdoesnotleadtothepairing

ofunpaired3delectrons.Therefore,itundergoes hybridization.

Since there are 2 unpaired electrons in this case, due to weak field ligand so, it is

paramagneticinnature.

6. is paramagnetic while is diamagnetic though both are

tetrahedral.Why?

Ans.Though both and are tetrahedral, their magnetic characters

aredifferent.Thisisduetoadifferenceinthenatureofligandsleadingtoparamagnetism.

isaweakfieldligandanditdoesnotcausethepairingofunpaired3delectrons.Hence,

isparamagnetic.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 6/43

In ,Niisinthezerooxidationstatei.e.,ithasaconfigurationof .

ButCOisastrongfieldligand.Therefore,itcausesthepairingofunpaired3delectrons.Also,

itcausesthe4selectronstoshift to the3dorbital, therebygivingriseto hybridization.

Sincenounpairedelectronsarepresentinthiscase, isdiamagnetic.

7. is strongly paramagnetic whereas is weakly

paramagnetic.Explain.

Ans.Inboth and ,Feexistsinthe+3oxidationstatei.e.,in

configuration.

Since is a strong field ligand, it causes the pairing of unpaired electrons. Therefore,

thereisonlyoneunpairedelectronleftinthed-orbital.

Therefore,

=1.732BM

On the other hand, is aweak field ligand. Therefore, it cannot cause the pairing of

electrons.Thismeansthatthenumberofunpairedelectronsis5.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 7/43

Therefore,

=6BM

Thus, it is evident that is strongly paramagnetic, while is

weaklyparamagnetic.

8. Explain is an inner orbital complex whereas is an

outerorbitalcomplex.

Ans.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 8/43

9.Predictthenumberofunpairedelectronsinthesquareplanar ion.

Ans.

Inthiscomplex,Pt is inthe+2state. It formsasquareplanarstructure.Thismeansthat it

undergoes hybridization.Now,theelectronicconfigurationofPd(+2)is .

beingastrongfield ligandcauses thepairingofunpairedelectrons.Hence, thereare

nounpairedelectronsin .

10. The hexaquo manganese (II) ion contains five unpaired electrons, while the

hexacyanoioncontainsonlyoneunpairedelectron.ExplainusingCrystalFieldTheory.

Ans.

Hence,hexaaquomanganese (II) ionhas fiveunpairedelectrons,whilehexacyano ionhas

onlyoneunpairedelectron.Sopairingtakesplaceandlowspincomplexesareformedwith

this1unpairedelectron.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 9/43

11. Calculate the overall complex dissociation equilibrium constant for the

ion,giventhat forthiscomplexis

Ans. =

The overall complex dissociation equilibrium constant is the reciprocal of the overall

stabilityconstant, .

ChapterEndQuestion

1.ExplainthebondingincoordinationcompoundsintermsofWerner'spostulates.

Ans.Werner'spostulatesexplainthebondingincoordinationcompoundsasfollows:

(i) A metal exhibits two types of valencies namely, primary and secondary valencies.

Primaryvalenciesaresatisfiedbynegative ionswhilesecondaryvalenciesaresatisfiedby

bothnegativeandneutralions.

(Inmodern terminology, theprimaryvalency corresponds to theoxidationnumberof the

metal ion,whereas the secondary valency refers to the coordinationnumber of themetal

ion.

(ii)Ametalionhasadefinitenumberofsecondaryvalenciesaroundthecentralatom.Also,

thesevalenciesprojectinaspecificdirectioninthespaceassignedtothedefinitegeometry

ofthecoordinationcompound.

(iii)Primaryvalenciesareusuallyionizable,whilesecondaryvalenciesarenon-ionizable.

2. solutionmixedwith solutionin1:1molarratiogivesthetestof

ionbut solutionmixedwithaqueousammoniain1:4molarratiodoesnot

givethetestof ion.Explainwhy?

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 10/43

Ans.

Both the compounds i.e., and fall

underthecategoryofadditioncompoundswithonlyonemajordifferencei.e.,theformeris

anexampleofadoublesalt,whilethelatterisacoordinationcompound.

Adoublesaltisanadditioncompoundthatisstableinthesolidstatebutthatwhichbreaks

up into its constituent ions in the dissolved state. These compounds exhibit individual

properties of their constituents. For e.g. breaks into

and ions.Hence,itgivesapositivetestfor ions.

Acoordinationcompoundisanadditioncompoundwhichretainsitsidentityinthesolidas

wellasinthedissolvedstate.However,theindividualpropertiesoftheconstituentsarelost.

Thishappensbecause doesnotshowthetestfor .Theions

presentinthesolutionof are and .

3. Explain with two examples each of the following: coordination entity, ligand,

coordinationnumber,coordinationpolyhedron,homolepticandheteroleptic.

Ans.(i)Coordinationentity:

A coordination entity is an electrically charged radical or species carrying a positive or

negativecharge.Inacoordinationentity,thecentralatomorionissurroundedbyasuitable

numberofneutralmoleculesornegativeions(calledligands).Forexample:

=cationiccomplex

=anioniccomplex

=neutralcomplex

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 11/43

(ii)Ligands

The neutral molecules or negatively charged ions that surround the metal atom in a

coordinationentityoracoordinalcomplexareknownasligands.Forexample, ,

Cl-, OH- . Ligands are usually polar in nature and possess at least one unshared pair of

valenceelectrons.

(iii)Coordinationnumber:

Thetotalnumberofligands(eitherneutralmoleculesornegativeions)thatgetattachedto

thecentralmetalatominthecoordinationsphereiscalledthecoordinationnumberofthe

centralmetalatom.Itisalsoreferredtoasitsligancy.

Forexample:

(a) Inthecomplex, , thereas sixchloride ionsattached toPt in thecoordinate

sphere.Therefore,thecoordinationnumberofPtis6.

(b)Similarly,inthecomplex ,thecoordinationnumberofthecentralatom

(Ni)is4.

(vi)Coordinationpolyhedron:

Coordinationpolyhedronsaboutthecentralatomcanbedefinedasthespatialarrangement

oftheligandsthataredirectlyattachedtothecentralmetalioninthecoordinationsphere.

Forexample:

(a)

(b)Tetrahedral

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 12/43

(v)Homolepticcomplexes:

These are those complexes in which themetal ion is bound to only one kind of a donor

group.Foreg: etc.

(vi)Heterolepticcomplexes:

Heterolepticcomplexesare thosecomplexeswhere thecentralmetal ion isboundtomore

thanonetypeofadonorgroup.

Fore.g.:

4.Whatismeantbyunidentate,didentateandambidentateligands?Givetwoexamples

foreach.

Ans.A ligandmay contain one ormore unshared pairs of electronswhich are called the

donorsitesof ligands.Now,dependingon thenumberof thesedonorsites, ligandscanbe

classifiedasfollows:

(a)Unidentateligands:Ligandswithonlyonedonorsitesarecalledunidentateligands.For

e.g., ,Cl-etc.

(b)Didentate ligands:Ligands thathave twodonorsitesarecalleddidentate ligands.For

e.g.,

(a)Ethane-1,2-diamine

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 13/43

(b)Oxalateion

(c)Ambidentateligands:

Ligands that canattach themselves to thecentralmetalatom through twodifferentatoms

arecalledambidentateligands.Forexample:

(a)

(ThedonoratomisN)

(Thedonoratomisoxygen)

(b)

(ThedonoratomisS)

(ThedonoratomisN)

5.Specifytheoxidationnumbersofthemetalsinthefollowingcoordinationentities:

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 14/43

(i)

(ii)

(iii)

(iv)

(v)

Ans.(i)

LettheoxidationnumberofCobex.

Thechargeonthecomplexis+2.

(ii)

LettheoxidationnumberofPtbex.

Thechargeonthecomplexis–2.

x+4(–1)=–2

x=+2

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 15/43

(iv)

6.UsingIUPACnormswritetheformulasforthefollowing:

(i)Tetrahydroxozincate(II)

(ii)Potassiumtetrachloridopalladate(II)

(iii)Diamminedichloridoplatinum(II)

(iv)Potassiumtetracyanonickelate(II)

(v)Pentaamminenitrito-O-cobalt(III)

(vi)Hexaamminecobalt(III)sulphate

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 16/43

(vii)Potassiumtri(oxalato)chromate(III)

(viii)Hexaammineplatinum(IV)

(ix)Tetrabromidocuprate(II)

(x)Pentaamminenitrito-N-cobalt(III)

Ans.(i)

(ii)

(iii)

(iv)

(v)

(vi)

(vii)

(viii)

(ix)

(x)

7.UsingIUPACnormswritethesystematicnamesofthefollowing:

(i)

(ii)

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 17/43

(iii)

(iv)

(v)

(vi)

(vii)

(viii)

(ix)

Ans.(i)Hexaamminecobalt(III)chloride

(ii)Diamminechlorido(methylamine)platinum(II)chloride

(iii)Hexaaquatitanium(III)ion

(iv)Tetraamminechloridonitrito-N-Cobalt(III)chloride

(v)Hexaaquamanganese(II)ion

(vi)Tetrachloridonickelate(II)ion

(vii)Hexaamminenickel(II)chloride

(viii)Tris(ethane-1,2-diammine)cobalt(III)ion

(ix)Tetracarbonylnickel(0)

8. List various types of isomerism possible for coordination compounds, giving an

exampleofeach.

Ans.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 18/43

(a)Geometricisomerism:

This typeof isomerism is common inheteroleptic complexes. It arisesdue to thedifferent

possiblegeometricarrangementsoftheligands.Forexample:

(b)Opticalisomerism:

Thistypeof isomerismarises inchiralmolecules. Isomersaremirrorimagesofeachother

andarenon-superimposable.

(c) Linkage isomerism: This type of isomerism is found in complexes that contain

ambidentateligands.Forexample:

and

YellowformRedform

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 19/43

(d)Coordinationisomerism:

This type of isomerism arises when the ligands are interchanged between cationic and

anionicentitiesofdiffernetmetalionspresentinthecomplex.

and

(e)Ionizationisomerism:

Thistypeofisomerismariseswhenacounterionreplacesaligandwithinthecoordination

sphere. Thus, complexes that have the same composition, but furnish different ionswhen

dissolvedinwaterarecalledionizationisomers.Fore.g.,[Co(NH3)5SO4]Brand

[Co(NH3)5Br]SO4.

(f)Solvateisomerism:

Solvateisomersdifferbywhetherornotthesolventmoleculeisdirectlybondedtothemetal

ionormerelypresentasafreesolventmoleculeinthecrystallattice.

VioletBlue-greenDarkgreen

9.Howmanygeometricalisomersarepossibleinthefollowingcoordinationentities?

(i)

(ii)

Ans.(i)For ,nogeometricisomerispossibleasitisabidentateligand.

(ii)

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 20/43

Twogeometricalisomersarepossible.

10.Drawthestructuresofopticalisomersof:

(i)

(ii)

(iii)

Ans.(i)

(ii)

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 21/43

(iii)

11.Drawalltheisomers(geometricalandoptical)of:

(i)

(ii)

(iii)

Ans.(i)

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 22/43

Intotal,threeisomersarepossible.

(ii)

Trans-isomersareopticallyinactive.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 23/43

Cis-isomersareopticallyactive.

(iii)

12.Write all the geometrical isomers of andhowmanyof

thesewillexhibitopticalisomers?

Ans.

From the above isomers, none will exhibit optical isomers. Tetrahedral complexes rarely

show optical isomerization. They do so only in the presence of unsymmetrical chelating

agents.

13.Aqueouscoppersulphatesolution(blueincolour)gives:

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 24/43

(i)agreenprecipitatewithaqueouspotassiumfluoride,and

(ii)abrightgreensolutionwithaqueouspotassiumchloride

Explaintheseexperimentalresults.

Ans.Aqueous existsas .Itisblueincolourduetothepresence

of

ions.

(i)WhenKFisadded:

(ii)WhenKClisadded:

Inboththesecases,theweakfieldligandwaterisreplacedbythe and ions.

14.WhatisthecoordinationentityformedwhenexcessofaqueousKCNisaddedtoan

aqueoussolutionofcoppersulphate?Whyisitthatnoprecipitateofcoppersulphideis

obtainedwhen ispassedthroughthissolution?

Ans.

i.e.,

Thus,thecoordinationentityformedintheprocessis . is

averystablecomplex,whichdoesnotionizetogive ionswhenaddedtowater.Hence,

ionsarenotprecipitatedwhen ispassedthroughthesolution.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 25/43

15.Discussthenatureofbondinginthefollowingcoordinationentitiesonthebasisof

valencebondtheory:

(i)

(ii)

(iii)

(iv)

Ans.(i) In the above coordination complex, iron exists in the +II oxidation

state.

:Electronicconfigurationis

Orbitalsof ion:

As isastrongfieldligand,itcausesthepairingoftheunpaired3delectrons.

Sincetherearesix ligandsaroundthecentralmetal ion, themostfeasiblehybridizationis

.

hybridizedorbitalsof are:

6electronpairsfrom ionsoccupythesixhybrid orbitals.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 26/43

Then,

Hence,thegeometryofthecomplexisoctahedralandthecomplexisdiamagnetic(asthere

arenounpairedelectrons).

(ii)

Inthiscomplex,theoxidationstateofFeis+3.

Orbitalsof ion:

Thereare6F-ions.Thus,itwillundergo or hybridization.As isaweakfield

ligand, it does not cause the pairing of the electrons in the 3d orbital. Hence, the most

feasiblehybridizationis .

hybridizedorbitalsofFeare:

Hence,thegeometryofthecomplexisfoundtobeoctahedral.

(iii)

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 27/43

Cobaltexistsinthe+3oxidationstateinthegivencomplex.

Orbitalsof ion:

Oxalate is a weak field ligand. Therefore, it cannot cause the pairing of the 3d orbital

electrons. As there are 6 ligands, hybridization has to be either or

hybridization.

hybridizationof :

The6electronpairsfromthe3oxalateions(oxalateanionisabidentateligand)occupythese

orbitals.

Hence,thegeometryofthecomplexisfoundtobeoctahedral.

(iv)

Cobaltexistsinthe+3oxidationstate.

Orbitalsof ion:

Again,fluorideionisaweakfieldligand.Itcannotcausethepairingofthe3delectrons.Asa

result,the ionwillundergo hybridization.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 28/43

hybridizedorbitalsof ionare:

Hence,thegeometryofthecomplexisoctahedralandparamagnetic.

16.Drawfiguretoshowthesplittingofdorbitalsinanoctahedralcrystalfield.

Ans.

The splitting of the d orbitals in an octahedral field takes palce in such a way that

experience a rise in energy and form the level, while and

experienceafallinenergyandformthe level.

ChapterEndQuestion

17.Whatisspectrochemicalseries?Explainthedifferencebetweenaweakfieldligand

andastrongfieldligand.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 29/43

Ans.Aspectrochemicalseriesisthearrangementofcommonligandsintheincreasingorder

oftheirfieldstrengthandcrystal-fieldsplittingenergy(CFSE)values.Theligandspresenton

theR.H.SoftheseriesarestrongfieldligandswhilethatontheL.H.Sareweakfieldligands.

Also, strong field ligands cause higher splitting in the d orbitals than weak field ligands.

Strongligandsareabletoproducestrongfieldwhereasweakligandsproduceweakfield.

Weak ligands can not cause pairing of electrons and form high spin complexes whereas

strongfieldligandscancausepairingofelectronsandthusformlowspincomplexes.

18. What is crystal field splitting energy? How does the magnitude of decide the

actualconfigurationofd-orbitalsinacoordinationentity?

Ans.Thedifferencebetweenenergiesoftwosetsofd-orbitalsiscalledcrystalfieldsplitting

energyi.e.deltanote.Thedegenerated-orbitals(inasphericalfieldenvironment)splitinto

twolevelsi.e., and inthepresenceofligands.Thesplittingofthesedegeneratelevels

duetothepresenceofligandsiscalledthecrystal-fieldsplittingwhiletheenergydifference

betweenthetwolevels( and )iscalledthecrystal-fieldsplittingenergy.Itisdenoted

by .

Aftertheorbitalshavesplit,thefillingoftheelectronstakesplace.After1electron(each)has

beenfilledinthethree orbitals,thefillingofthefourthelectrontakesplaceintwoways.

Itcanenterthe orbital(givingriseto likeelectronicconfiguration)orthepairing

of the electrons can take place in the orbitals (giving rise to like electronic

configuration). If the value of a ligand is less than the pairing energy (P), then the

electronsenterthe orbital.Ontheotherhand,ifthe valueofaligandismorethanthe

pairingenergy(P),thentheelectronsenterthe orbital.

Although orbital splitting energies are not sufficiently large to force pairing so low spin

configurationarerarelyobserved.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 30/43

19. isparamagneticwhile isdiamagnetic.Explainwhy?

Ans.Cr is in the+3oxidation state i.e., configuration.Also, is aweak field ligand

thatdoesnotcausethepairingoftheelectronsinthe3dorbital.

Therefore, it undergoes hybridization and the electrons in the 3d orbitals remain

unpaired.Hence,itisparamagneticinnature.

In ,Niexistsinthe+2oxidationstatei.e., configuration.

:

isa strong field ligand. It causes thepairingof the3d orbitalelectrons.Then,

undergoes hybridization.

Astherearenounpairedelectrons,itisdiamagneticwithsquareplanarshape.

20.Asolutionof isgreenbutasolutionof iscolourless.

Explain.

Ans. In , is a weak field ligand. Therefore, there are unpaired

electrons in . In this complex, the d electrons from the lower energy level can be

excited to the higher energy level i.e., the possibility ofd - d transition is present. Hence,

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 31/43

light is absorbed from visible region and complementary green colour is radiated. So,

isgreencoloured.

In ,theelectronsareallpairedas isastrongfieldligand.Therefore,d-

dtransitionisnotpossiblein .Hence,itiscolourless.

21. and areofdifferentcoloursindilutesolutions.Why?

Ans.The colour of a particular coordination compound depends on themagnitude of the

crystal-fieldsplittingenergy, .ThisCFSE in turndependson thenatureof the ligand. In

caseof and ,thecolourdiffersbecausethereisadifference

intheCFSE.Now, isastrongfield ligandhavingahigherCFSEvalueascomparedto

theCFSEvalueofwater.Thismeansthattheabsorptionofenergyfromvisibleregionoccurs

fortheintrad-dtransitionandcomplementarycoloursareradiated.Hence,thetransmitted

colouralsodiffers.

22.Discussthenatureofbondinginmetalcarbonyls.

Ans.Themetal-carbonbondsinmetalcarbonylshaveboth and characters. bondis

formedwhenthecarbonylcarbondonatesalonepairofelectronstothevacantorbitalofthe

metal. A bond is formed by the donation of a pair of electrons from the filledmetal d

orbitalintothevacantanti-bonding orbital(alsoknownasbackbondingofthecarbonyl

group). The bond strengthens the bond and vice-versa. Thus, a synergic effect is

createdduetothismetal-ligandbonding.Thissynergiceffectstrengthensthebondbetween

COandthemetal.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 32/43

23. Give the oxidation state, d-orbital occupation and coordination number of the

centralmetalioninthefollowingcomplexes:

(i)

(ii)cis-

(iii)

(iv)

Ans.(i)

ThecentralmetalionisCo.

Itscoordinationnumberis6.

Theoxidationstatecanbegivenas:

x–6=–3

x=+3

Thedorbitaloccupationfor is .

(ii)cis-

ThecentralmetalionisCr.

Thecoordinationnumberis6.

Theoxidationstatecanbegivenas:

x+2(0)+2(–1)=+1

x–2=+1

x=+3

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 33/43

Thedorbitaloccupationfor is .

(iii)

ThecentralmetalionisCo.

Thecoordinationnumberis4.

Theoxidationstatecanbegivenas:

x–4=–2

x=+2

Thedorbitaloccupationfor is .

(iv)

ThecentralmetalionisMn.

Thecoordinationnumberis6.

Theoxidationstatecanbegivenas:

x+0=+2

x=+2

ThedorbitaloccupationforMnis .

24.WritedowntheIUPACnameforeachof thefollowingcomplexesandindicatethe

oxidation state, electronic configuration and coordination number. Also give

stereochemistryandmagneticmomentofthecomplex:

(i)

(ii)

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 34/43

(iii)

(iv)

(v)

Ans.(i)Potassiumdiaquadioxalatochromate(III)trihydrate.

Oxidationstateofchromium=3

Electronicconfiguration:

Coordinationnumber=6

Shape:octahedral

Stereochemistry:

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 35/43

Magneticmoment,

(ii)

IUPACname:Pentaamminechloridocobalt(III)chloride

OxidationstateofCo=+3

Coordinationnumber=6

Shape:octahedral.

Electronicconfiguration: .

Stereochemistry:

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 36/43

MagneticMoment=0

(iii)

IUPACname:Trichloridotripyridinechromium(III)

Oxidationstateofchromium=+3

Electronicconfigurationfor

Coordinationnumber=6

Shape:octahedral.

Stereochemistry:

Bothisomersareopticallyactive.Therefore,atotalof4isomersexist.

Magneticmoment,

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 37/43

(iv)

IUPACname:Caesiumtetrachloroferrate(III)

OxidationstateofFe=+3

Electronicconfigurationof

Coordinationnumber=4

Shape:tetrahedral

Stereochemistry:opticallyinactive

Magneticmoment:

(v)

Potassiumhexacyanomanganate(II)

Oxidationstateofmanganese=+2

Electronicconfiguration:

Coordinationnumber=6

Shape:octahedral.

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 38/43

Streochemistry:opticallyinactive

Magneticmoment,

=1.732

25.Whatismeantbystabilityofacoordinationcompoundinsolution?Statethefactors

whichgovernstabilityofcomplexes.

Ans.Thestabilityofacomplexinasolutionreferstothedegreeofassociationbetweenthe

two species involved ina stateof equilibrium.Stability canbeexpressedquantitatively in

termsofstabilityconstantorformationconstant.

Forthisreaction,thegreaterthevalueofthestabilityconstant,thegreateristheproportion

of inthesolution.

Stabilitycanbeoftwotypes:

(a)Thermodynamicstability:

Theextenttowhichthecomplexwillbeformedorwillbetransformedintoanotherspecies

atthepointofequilibriumisdeterminedbythermodynamicstability.

(b)Kineticstability:

Thishelpsindeterminingthespeedwithwhichthetransformationwilloccurtoattainthe

stateofequilibrium.

Factorsthataffectthestabilityofacomplexare:

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 39/43

(a)Chargeonthecentralmetalion:Thegreater thechargeon thecentralmetal ion, the

greateristhestabilityofthecomplex.

(b)Basicnatureoftheligand:Amorebasicligandwillformamorestablecomplex.

(c)Presenceofchelaterings:Chelationincreasesthestabilityofcomplexes.

26.Whatismeantbythechelateeffect?Giveanexample.

Ans.Whenaligandattachestothemetalioninamannerthatformsaring,thenthemetal-

ligand association is found to bemore stable. In otherwords,we can say that complexes

containingchelateringsaremorestablethancomplexeswithoutrings.Thisisknownasthe

chelateeffect.

Forexample:

27.Discussbrieflygivinganexampleineachcasetheroleofcoordinationcompounds

in:

(i)biologicalsystem

(ii)medicinalchemistry

(iii)analyticalchemistry

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 40/43

(iv)extraction/metallurgyofmetals

Ans.(i)Roleofcoordinationcompoundsinbiologicalsystems:

Weknowthatphotosynthesisismadepossiblebythepresenceofthechlorophyllpigment.

This pigment is a coordination compound ofmagnesium. In the humanbiological system,

several coordination compounds play important roles. For example, the oxygen-carrier of

blood,i.e.,haemoglobin,isacoordinationcompoundofiron.

(ii)Roleofcoordinationcompoundsinmedicinalchemistry:

Certaincoordinationcompoundsofplatinum(forexample,cis-platin)areusedforinhibiting

thegrowthoftumours.

(iii)Roleofcoordinationcompoundsinanalyticalchemistry:

During salt analysis, a number of basic radicals are detected with the help of the colour

changes they exhibit with different reagents. These colour changes are a result of the

coordinationcompoundsorcomplexesthatthebasicradicalsformwithdifferentligands.

(iii)Roleofcoordinationcompoundsinextractionormetallurgyofmetals:

Theprocess of extraction of someof themetals from their ores involves the formation of

complexes. For example, in aqueous solution, gold combines with cyanide ions to form

.Fromthissolution,goldislaterextractedbytheadditionofzincmetal.

28.Howmanyionsareproducedfromthecomplex insolution?

(i)6

(ii)4

(iii)3

(iv)2

Ans.(iii)Thegivencomplexcanbewrittenas .

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 41/43

Thus, alongwithtwoCl-ionsareproduced.

29.Amongstthefollowingionswhichonehasthehighestmagneticmomentvalue?

(i)

(ii)

(iii)

Ans.(i)No.ofunpairedelectronsin =3

Then,

(ii)No.ofunpairedelectronsin =4

Then,

(iii)No.ofunpairedelectronsin

Hence, hasthehighestmagneticmomentvalue.

30.Theoxidationnumberofcobaltin is

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 42/43

(i)+1

(ii)+3

(iii)-1

(iv)-3

Ans.WeknowthatCOisaneutralligandandKcarriesachargeof+1.

Therefore, the complex can be written as . Therefore, the oxidation

numberofCointhegivencomplexis-1.Hence,option(iii)iscorrect.

31.Amongstthefollowing,themoststablecomplexis

(i)

(ii)

(iii)

(iv)

Ans.We know that the stability of a complex increases by chelation. Therefore, themost

stablecomplexis .

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM

MaterialdownloadedfrommyCBSEguide.com. 43/43

32. What will be the correct order for the wavelengths of absorption in the visible

regionforthefollowing:

Ans.Thecentralmetal ioninall thethreecomplexesis thesame.Therefore,absorptionin

thevisibleregiondependsontheligands.TheorderinwhichtheCFSEvaluesoftheligands

increasesinthespectrochemicalseriesisasfollows:

Thus,theamountofcrystal-fieldsplittingobservedwillbeinthefollowingorder:

Hence,thewavelengthsofabsorptioninthevisibleregionwillbeintheorder:

osbincbse.com

OSBINCBSE.COM

OSBINCBSE.COM

OSBINCBSE.COM