Question Paper 2015 Set-1 Class-12 Chemistry osbincbse.com...
Transcript of Question Paper 2015 Set-1 Class-12 Chemistry osbincbse.com...
MaterialdownloadedfrommyCBSEguide.com. 1/15
QuestionPaper2015Set-1
Class-12Chemistry
Time:3Hours,MaximumMarks:70
GeneralInstructions:
1.Allquestionsarecompulsory.
2.Q.No.1to5areveryshortanswerquestionsandcarry1markeach.
3.Q.No.6to10areshortanswerquestionsandcarry2markseach.
4.Q.No.11to22arealsoshortanswerquestionsandcarry3markseach.
5.Q.No.23isavaluebasedquestionandcarry4marks.
6.Q.No.24to26arelonganswerquestionsandcarry5markseach.
7.Uselogtablesifnecessary,useofcalculatorisnotallowed.
1.Whatistheno.ofatomsperunitcell(z)inabody-centredcubicstructure?
Ans.2
2.Inreferencetosurfacechemistry,definedialysis.
Ans.Itisaprocessofremovingadissolvedsubstancefromacolloidalsolutionbymeansof
diffusionthroughasuitablemembrane.
3.WhatistheIUPACnameofthecomplex[Ni(NH ) ]Cl ?
Ans.Hexaamninenickel(II)chloride
4.Drawthestructureof3-methylpentanal.
Ans.
5.Completethefollowingreactionequation:
C H N Cl+H PO +H O
Ans.
osbincbse.comPage 1
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 2/15
(whereArisC6H5)
6.Defineosmoticpressureofasolution.Howistheosmoticpressurerelatedtothe
concentrationofasoluteinasolution?
Ans.Theexternalpressurewhichisappliedonsolutionsidetostoptheflowofsolvent
acrossthesemi-permeablemembrane.Theosmoticpressureisdirectlyproportionalto
concentrationofthesolution. =CRT
7.Definethefollowingterms:
(i)Half-lifeofareaction(t½)
(ii)Rateconstant(k)
Ans.(i)Thehalf-lifeofareactionisthetimeinwhichtheconcentrationofareactantis
reducedtoonehalfofitsinitialconcentration.
(ii)Rateconstantistherateofreactionwhentheconcentrationofthereactantisunity.
8.Drawthestructuresofthefollowing:(i)H SO
(ii)
Ans.(i)
(ii)
osbincbse.comPage 2
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 3/15
9.Whatismeantby‘disproportionation’?Giveanexampleofadisproportionation
reactioninaqueoussolution.
OR
Suggestreasonsforthefollowingfeaturesoftransitionmetalchemistry:
(i)Thetransitionmetalsandtheircompoundsareusuallyparamagnetic.
(ii)Thetransitionmetalsexhibitvariableoxidationstates.
Ans.Disproportionation:Thereactioninwhichanelementundergoesself-oxidationand
selfreduction
simultaneously.Forexample:
2Cu+(aq) +(aq)+Cu(s)
10.Explainthemechanismofdehydrationstepsofethanol:-
Ans.
11.Definethefollowing:
(i)Schottkydefect
osbincbse.comPage 3
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 4/15
(ii)Frenkeldefect
(iii)F-centre
Ans.(i)Thedefectinwhichequalnumberofcationsandanionsaremissingfromthelattice.
(ii)Duetodislocationofsmallerionfromitsnormalsitetoaninterstitialsite.
(iii)Anionicvacanciesareoccupiedbyunpairedelectron.
12.45gofethyleneglycol(C H O )ismixedwith600gofwater.Calculate
(i)thefreezingpointdepressionand
(ii)thefreezingpointofthesolution
(Given:Kfofwater=1.86Kkgmol )
Ans.(i)
2.325Kor2.325
(ii) =2.325
O - =2.325
=-2.325 or270.675K
13.Therateconstantsofareactionat500Kand700Kare0.02s and0.07s
respectively.Calculatethevalueofactivationenergy,Ea.(R=8.314JK mol )
Ans. =
log =
osbincbse.comPage 4
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 5/15
0.544= 5.714 /19.15
=0.544 19.15/5.714 =18230.8K
14.Definethefollowingterms:
(i)Electrophoresis
(ii)Adsorption
(iii)Shapeselectivecatalysis
Ans.(i)Themovementofcolloidalparticlesunderanappliedelectricpotentialtowards
oppositelychargedelectrodeiscalledelectrophoresis.
(ii)Theaccumulationofmolecularspeciesatthesurfaceratherthaninthebulkofasolidor
liquidistermedadsorption.
(iii)Thecatalyticreactionthatdependsupontheporestructureofthecatalystandthesize
ofthereactantandproductmoleculesiscalledshape-selectivecatalysis.
15.Outlinetheprinciplesofrefiningofmetalsbythefollowingmethods:
(i)Distillation
(ii)Zonerefining
(iii)Electrolysis
OR
Writedownthereactionstakingplaceindifferentzonesintheblastfurnaceduring
theextractionofiron.Howispigirondifferentfromcastiron?
Ans.(i)Theimpuremetalisevaporatedtoobtainthepuremetalasdistillate.
(ii)Thismethodisbasedontheprinciplethattheimpuritiesaremoresolubleinthemelt
thaninthesolidstateofthemetal.
(iii)Theimpuremetalismadetoactasanode.Astripofthesamemetalinpureformisused
ascathode.Theyareputinasuitableelectrolyticbathcontainingsolublesaltofthesame
metal.Themorebasicmetalremainsinthesolutionandthelessbasiconesgototheanode
mud.
OR
osbincbse.comPage 5
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 6/15
3 +CO +
(Ironore)
+CO
(limestone)
CaO (Slag)
FeO+CO Fe+
C+ Fe+
Coke
FeO+C Fe+CO
Castironhaslowercarboncontent(about3%)thanpigiron/castironishard&brittle
whereaspigironissoft.
16.Whatislanthanoidcontraction?Whataretheconsequencesoflanthanoid
contraction?
Ans.ThesteadydecreaseinatomicradiifromLatoLuduetoimperfectshieldingof4f–
orbital.
Consequences–
(i)Membersofthirdtransitionserieshavealmostidenticalradiiascorespondingmembers
ofsecondtransitionseries.
(ii)Difficultyinseparation.
17.Indicatethetypesofisomerismexhibitedbythefollowingcomplexes:
(i)[Co(NH ) (NO2)]
(ii)[Co(en) ]Cl (en=ethylenediamine)
(iii)[Pt(NH )2Cl ]
Ans.(a)Linkageisomerism
(b)Opticalisomerism
(c)Cis-trans/Geometricalisomerism
18.NamethefollowingaccordingtoIUPACsystem:
osbincbse.comPage 6
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 7/15
(i)
(ii)
(iii)
Ans.(a)Butan–2–ol
(b)2–bromotoluene
(c)2,2-dimethylchlorpropane
19.Howarethefollowingconversionscarriedout?
(i)Propenetopropane-2-ol
(ii)BenzylchloridetoBenzylalcohol
(iii)Anisoletop-Bromoanisole
Ans.(i)
(ii)
osbincbse.comPage 7
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 8/15
(iii)
20.Anaromaticcompound‘A’ontreatmentwithaqueousammoniaandheatingforms
compound‘B’whichonheatingwith andKOHformsacompound‘C’ofmolecular
formula .WritethestructuresandIUPACnamesofcompoundsA,BandC.
Ans.A-BenzoicAcid
B-Benzamide
C-Aniline
21.Howarevitaminsclassified?Namethevitaminresponsibleforthecoagulationof
blood.
Ans.Fatsolublevitamin-VitaminA,D
Watersolublevitamin-VitaminB,C
VitaminK
osbincbse.comPage 8
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 9/15
22.Writethenamesandstructuresofthemonomersofthefollowingpolymers:
(i)Buna-S
(ii)Neoprene
(iii)Teflon
Ans.(i) =CH=CH= and
=
1,3-ButadieneStydrene
(ii)
Chloroprene/2-Chloro-1,3-Butadine
(iii)
Tetrafluroethene
23.Rameshwenttoadepartmentalstoretopurchasegroceries.Ononeofshelveshe
noticedsugar-freetablets.Hedecidedtobuythemforhisgrandfatherwhowasa
diabetic.Therewerethreetypesofsugar-freetablets.Rameshdecidedtobuysucrolose
whichwasgoodforhisgrandfather’shealth.
(i)NameanothersugarfreetabletwhichRameshdidnotbuy.
(ii)Wasitrighttopurchasesuchmedicineswithoutdoctor’sprescription?
(iii)WhatqualityofRameshisreflectedabove?
Ans.(i)Aspartame,Saccharin(anyone)
(ii)No
(iii)Socialconcern,empathy,concern,socialawareness.
24.a)Definethefollowingterms:
osbincbse.comPage 9
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 10/15
(i)Molarconductivity(^m)
(ii)Secondarybatteries
(iii)Fuelcell
(b)Statethefollowinglaws:
(i)Faradayfirstlawofelectrolysis
(ii)Kohlrausch’slawofindependentmigrationofions
OR
(a)Definethetermdegreeofdissociation.Writeanexpressionthatrelatesthemolar
conductivityofaweakelectrolytetoitsdegreeofdissociation.
(b)Forthecellreaction
Ni(s)| (aq)|| (aq)|Ag(s)
Calculatetheequilibriumconstantat25°C.Howmuchmaximumworkwouldbe
obtainedbyoperationofthiscell?
E° /Ni=0.25VandE°
Ag+/Ag=0.80V.
Ans.(a)(i)Molarconductivityofasolutionatagivenconcentrationistheconductanceofthe
volumeVofsolutioncontainingonemoleofelectrolytekeptbetweentwoelectrodeswith
areaofcrosssectionAanddistanceofunitlength.
(ii)Secondarybattery-canberechargedbypassingcurrentthroughitinoppositedirection
sothatitcanbeusedagain.
(iii)Galvaniccellsthataredesignedtoconverttheenergyofcombustionoffuelslike
hydrogen,methane,methanol,etc.directlyintoelectricalenergyarecalledfuelcells.
(b)(i)Theamountofchemicalreactionwhichoccursatanyelectrodeduringelectrolysisby
acurrentisproportionaltothequantityofelectricitypassedthroughtheelectrolyte(solution
ormelt).
(ii)Limitingmolarconductivityofanelectrolytecanberepresentedasthesumofthe
individualcontributionsoftheanionandcationoftheelectrolyte.
osbincbse.comPage 10
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 11/15
OR
(a)Degreeofdissociationistheextenttowhichelectrolytegetsdissociatedintoits
constituentions.
(b) cell= Ag+/Ag- Ni2+/Ni
=0.80V–0.25V
=0.55V
logKc=
=
logKc=18.644
=-nF cell
=-2 96500C 0.55V
=-106,150J
Max.work=+106150J
or106.150kJ
25.(a)Completethefollowingchemicalreactionequations:
(i)Cu+HNO (dilute)
(ii)P +NaOH+H2O
(b)(i)WhydoesR P=OexistbutR N=Odoesnot?(R=alkylgroup)
(ii)Whyisdioxygenagasbutsulphurasolid?
(iii)Whyarehalogenscoloured?
OR
(a)Writebalancedequationsforthefollowingreactions:
(i)Chlorinereactswithdryslakedlime.
(ii)CarbonreactswithconcentratedH SO .
osbincbse.comPage 11
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 12/15
(b)Describethecontactprocessforthemanufactureofsulphuricacidwithspecial
referencetothereactionconditions,catalystsusedandtheyieldintheprocess.
Ans.(a)(i)
(ii)C+ (conc.)
(b)i)Duetoabsenceofd-orbital,nitrogencannotexpanditsvalencybeyondfour.
(ii)Becauseofpπ–pπmultiplebondingindioxygenwhichisabsentinsulphur.
(iii)Duetoexcitationofelectronbyabsorptionofradiationfromvisibleregion.
OR
(a)(i)
(ii)C+ (conc.)
b)ItismanufacturedbyContactProcesswhichinvolvesfollowingsteps:
(i)burningofsulphurorsulphideoresinairtogenerate .
(ii)conversionof to bythereactionwithoxygeninthepresenceofacatalyst(
)
(iii)absorptionof in togiveOleum( ).Theoleumobtainedisdilutedto
givesulphuricacid
Reactioncondition–pressureof2barandtemperatureof720K
Catalystusedis
Yield–96–98%pure
26.(a)Describethefollowinggivingchemicalequations:
(i)De-carboxylationreaction
osbincbse.comPage 12
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 13/15
(ii)Friedel-Craftsreaction
(b)Howwillyoubringaboutthefollowingconversions?
(i)BenzoicacidtoBenzaldehyde
(ii)Benzenetom-Nitroacetophenone
(iii)Ethanolto3-Hydroxybutanal
OR
(a)Describethefollowingactions:
(i)Acetylation(ii)Aldolcondensation
(b)Writethemainproductinthefollowingequations:
(i)
(ii)
(iii)
Ans.(a)(i)Carboxylicacidslosecarbondioxidetoformhydrocarbonswhentheirsodium
saltsare
heatedwithsodalime(NaOHandCaO).
(ii)Whenthealkyl/acylgroupisintroducedatorthoandparapositionsbyreaction
withalkylhalide/acylhalideinthepresenceofanhydrousaluminiumchloride(aLewis
acid)ascatalyst.
osbincbse.comPage 13
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 14/15
(b)(i)
(ii)
(iii)
OR
(a)(i)Whentheacylgroupsareintroducedatorthoandparapositionsbyreactionwithacyl
halideinthepresenceofanhydrousaluminiumchloride(aLewisacid)ascatalyst.
(ii)Aldehydesandketoneshavingatleastone-hydrogenundergoareactioninthepresence
osbincbse.comPage 14
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM
MaterialdownloadedfrommyCBSEguide.com. 15/15
ofdilutealkaliascatalysttoform -hydroxyaldehydes(aldol)or -hydroxyketones
(ketol),respectively.
(b)(i)
(ii)
(iii)
YoucandownloaditasPDFfilefrommyCBSEguide.com
osbincbse.comPage 15
OSBINCBSE.COM
OSBINCBSE.COM
OSBINCBSE.COM