exercise multiple choice questions(mcqs) · 2020. 9. 15. · chapter 4 carbon and its compounds...

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CBSEClass10Science

NCERTExemplarSolutions

Chapter4

CarbonanditsCompounds

Multiple Choice Questions(MCQs)

1. Carbonexistsintheatmosphereintheformof

(a) carbonmonoxideonly

(b) carbonmonoxideintracesandcarbondioxide

(c) carbondioxideonly

(d) coal

Ans.(c)carbondioxideonly

2. Whichofthefollowingstatementsareusuallycorrectforcarboncompounds?These

(i) aregoodconductorsofelectricity

(ii) arepoorconductorsofelectricity

(iii) havestrongforcesofattractionbetweentheirmolecules

(iv) donothavestrongforcesofattractionbetweentheirmolecules

(a) (i)and(iii)

(b) (ii)and(iii)

(c) (i)and(iv)

(d) (ii)and(iv)

Ans.(d)(ii)and(iv)

Explanation:Organiccompoundaremadeofcovalentbonds.Thesebondshaveweaker

forcesofattraction.Covalentcompoundsarepoorconductorsofelectricity.

Exercise


3. Amoleculeofammonia(NH3)has

(a) onlysinglebonds

(b) onlydoublebonds

(c) onlytriplebonds

(d) twodoublebondsandonesinglebond

Ans.(a)Onlysinglebonds

Explanation:Thevalencyofnitrogenis3andthatofhydrogenisone.Threeatomsof

hydrogencombinewith1atomofnitrogentomakeammonia.Hence,therearethreesingle

bondsinammonia.

4. Buckminsterfullereneisanallotropicformof

(a) phosphorus

(b) sulphur

(c) carbon

(d) tin

Ans.(c)Carbon

5. Whichofthefollowingarecorrectstructuralisomersofbutane?

https://www.ncertbooks.guru/ncert-exemplar-problems-solutions-pdf/


(a) (i)and(iii)

(b) (ii)and(iv)

(c) (i)and(ii)

(d) (iii)and(iv)

Ans.(c)(i)and(ii)

Explanation:FormulaofbutaneisC4H10.Options(iii)and(iv)have8hydrogenatomseach,

hence,theyareincorrect.

6. Inthegivenreaction,alkalineKMnO4actsas

(a) reducingagent

(b) oxidisingagent

(c) catalyst

(d) dehydratingagent

Ans.(b)Oxidisingagent

Explanation:Twohydrogenatomsarereplacedbyanatomofoxygeninthisreaction.This

showsoxidizationofethanol.Additionofoxygenisbeingprovidedbypotassium


permanganate.

7. Oilsontreatingwithhydrogeninthepresenceofpalladiumornickelcatalystform

fats.Thisisanexampleof

(a) Additionreaction

(b) Substitutionreaction

(c) Displacementreaction

(d) Oxidationreaction

Ans.(a)Additionreaction

Explanation:Inthisreaction,hydrogenisaddedtooil.

8. Inwhichofthefollowingcompounds,—OHisthefunctionalgroup?

(a) Butanone

(b) Butanol

(c) Butanoicacid

(d) Butanal

Ans.(b)Butanol

Explanation:Compoundswith-OHasfunctionalgrouphave‘ol’assuffix.

9. Thesoapmoleculehasa

(a) hydrophilicheadandahydrophobictail

(b) hydrophobicheadandahydrophilictail

(c) hydrophobicheadandahydrophobictail

(d) hydrophilicheadandahydrophilictail


Ans.(a)Hydrophilicheadandhydrophobictail

Explanation:Oilandgreaseistrappedinsideamicellebecauseofhydrophobictail.

Hydrophilicheadmakestheoutersurfaceofmicelle.

Thus,amicelleiseasilywashedbywater.

10. Whichofthefollowingisthecorrectrepresentationofelectrondotstructureof

nitrogen?

(a)

(b)

(c)

(d)

Ans.(d)

Explanation:Inthisstructure,eachnitrogenatomgets8electrons.Thisisnotinthecase

ofotheroptions.

11. Structuralformulaofethyneis

(a)

(b)

Ans.(a)

Explanation:TheformulaofethyneisC2H2.


12. Identifytheunsaturatedcompoundsfromthefollowing

(i) Propane

(ii) Propene

(iii) Propyne

(iv) Chloropropane

(a) (i)and(ii)

(b) (ii)and(iv)

(c) (iii)and(iv)

(d) (ii)and(iii)

Ans.(d)(ii)and(iii)

Explanation:Propenehasonedoublebond,whilepropynehasonetriplebond.Hence,they

areunsaturatedcompounds.

13. Chlorinereactswithsaturatedhydrocarbonsatroomtemperatureinthe

(a) absenceofsunlight

(b) presenceofsunlight

(c) presenceofwater

(d) presenceofhydrochloricacid

Ans.(b)Presenceofsunlight

Explanation:Chlorinereactswithsaturatedhydrocarbonsinthepresenceofsunlightand

displaceshydrogenatomsonebyone.

14. Inthesoapmicelles

(a) theionicendofsoapisonthesurfaceoftheclusterwhilethecarbonchainisinthe


interiorofthecluster.

(b) ionicendofsoapisintheinterioroftheclusterandthecarbonchainisoutofthecluster.

(c) bothionicendandcarbonchainareintheinteriorofthecluster.

(d) bothionicendandcarbonchainareontheexteriorofthecluster.

Ans.(a)theionicendofsoapisonthesurfaceoftheclusterwhilethecarbonchainisinthe

interiorofthecluster.

15. PentanehasthemolecularformulaC5H12.Ithas

(a) 5covalentbonds

(b) 12covalentbonds

(c) 16covalentbonds

(d) 17covalentbonds

Ans.(c)16covalentbonds

Explanation:Followingisthestructuralformulaofpentane.Itshows16covalentbonds:

16. Structuralformulaofbenzeneis


Ans.(c)

Explanation: Formula of benzene is C6H6. In option c, all the arms of carbon atoms are

occupied.

17. Ethanolreactswithsodiumandformstwoproducts.Theseare

(a) sodiumethanoateandhydrogen

(b) sodiumethanoateandoxygen

(c) sodiumethoxideandhydrogen

(d) sodiumethoxideandoxygen

Ans.(c)Sodiumethoxideandhydrogen

Explanation:Thisreactioncanbeshownbyfollowingequation:


18. Thecorrectstructuralformulaofbutanoicacidis

Ans.(d)

Explanation:FormulaofbutanoicacidisC3H7COOH.

19. Vinegarisasolutionof

(a) 50%–60%aceticacidinalcohol

(b) 5%–8%aceticacidinalcohol

(c) 5%–8%aceticacidinwater

(d) 50%–60%aceticacidinwater

Ans.(c)5%-8%aceticacidinwater

20. Mineralacidsarestrongeracidsthancarboxylicacidsbecause

(i) mineralacidsarecompletelyionized

(ii) carboxylicacidsarecompletelyionized


(iii) mineralacidsarepartiallyionized

(iv) carboxylicacidsarepartiallyionized

(a) (i)and(iv)

(b) (ii)and(iii)

(c) (i)and(ii)

(d) (iii)and(iv)

Ans.(a)(i)and(iv)

Explanation:Mineralacidsarecompletelyionizedbutcarboxylicacidsarepartiallyionized.

Hence,mineralacidsarestrongeracidsthancarboxylicacids.

21. Carbonformsfourcovalentbondsbysharingitsfourvalenceelectronswithfour

univalentatoms,e.g.hydrogen.Aftertheformationoffourbonds,carbonattainsthe

electronicconfigurationof

(a) helium

(b) neon

(c) argon

(d) krypton

Ans.(b)Neon

Explanation:Electronicconfigurationofcarbonis2,4andaftersharingfourelectronsfrom

fourunivalentatoms,itselectronicconfigurationbecomes2,8whichissameasthatofNeon.

22. Thecorrectelectrondotstructureofawatermoleculeis

(a)


(b)

(c)

(d)

Ans.(c)

Explanation:Thisdotstructureshowsacompleteoctetafteroxygensharedtwoelectrons

withtwounivalentatomsofhydrogen.

23. Whichofthefollowingisnotastraightchainhydrocarbon?

(b)

Ans.(d)

Explanation:Inthisoption,threecarbonatomsaresharingelectronswithunivalentatoms.

Inotheroptions,onlytwocarbonatomsaresharingelectronswithunivalentatoms.

24. Whichamongthefollowingareunsaturatedhydrocarbons?

(i) H3C—CH2—CH2—CH3


(a) (i)and(iii)

(b) (ii)and(iii)

(c) (ii)and(iv)

(d) (iii)and(iv)

Ans.(c)(ii)and(iv)

Explanation:Thesecompoundsshowdoubleandtriplebonds.Hencetheyareunsaturated

hydrocarbons.

25. Whichofthefollowingdoesnotbelongtothesamehomologousseries?

(a) CH4

(b) C2H6

(c) C3H8

(d) C4H8

Ans.(d)C4H8

Explanation:ThegeneralformulaforthiscompoundisCnH2n,whilethatofotheroptionsis

CnH2n+2.

26. ThenameofthecompoundCH3—CH2—CHOis

(a) Propanal


(b) Propanone

(c) Ethanol

(d) Ethanal

Ans.(a)Propanal

Explanation:Thiscompoundhas asactiveradical.It'sanaldehyde.Hence,-alsuffix

isused.

27. TheheteroatomspresentinCH3—CH2—O—CH2—CH2Clare

(i) oxygen

(ii) carbon

(iii) hydrogen

(iv) chlorine

(a) (i)and(ii)

(b) (ii)and(iii)

(c) (iii)and(iv)

(d) (i)and(iv)

Ans.(d)(i)and(iv)

Explanation:Oxygenandchlorinearenotamongessentialcomponentsofhydrocarbons.

28. Whichofthefollowingrepresentssaponificationreaction?

(a)

(b)


(c)

(d)

Ans.(d)

Explanation:Whenesteristreatedwithanalkali,thereactiongivesethanolandsodium

ethanoate.Thisreactioniscalledsaponificationreaction.

29. Thefirstmemberofalkynehomologousseriesis

(a) ethyne

(b) ethene

(c) propyne

(d) methane

Ans.(a)Ethyne


Short Answer Questions

30. Drawtheelectrondotstructureofethyneandalsodrawitsstructuralformula.

Ans.

31. Writethenamesofthefollowingcompounds

Ans.Pentanoicacid

Ans.Butyne

Ans.Heptanal



Ans.Pentanol

32. Identifyandnamethefunctionalgroupspresentinthefollowingcompounds.

Ans.alcohol

Ans.carboxylicacid

Ans.Ketone

Ans.alkene

33. AcompoundXisformedbythereactionofacarboxylicacidC2H4O2andanalcohol

inpresenceofafewdropsofH2SO4.ThealcoholonoxidationwithalkalineKMnO4

followedbyacidificationgivesthesamecarboxylicacidasusedinthisreaction.Give

thenamesandstructuresof(a)carboxylicacid,(b)alcoholand(c)thecompoundX.

Also,writethereaction.

Ans.(a)Carboxylicacidisethanoicacidanditsstructuralformulaisasfollows:


(b) Alcoholisethanolanditsstructuralformulaisasfollows:

(c) CompoundXisanester(ethylethanoate)anditsstructuralformulaisasfollows:

34. Whydetergentsarebettercleansingagentsthansoaps?Explain.

Ans.Detergentsaregenerallyammoniumorsulphonatesaltsoflongchaincarboxylicacids.

Thechargedendsofthesecompoundsdonotforminsolubleprecipitatewithcalciumor

magnesiumions.Calciumandmagnesiumionsarepresentinhardwater.Duetothis,

detergentsareeffectiveeveninhardwater.Hence,detergentsarebettercleansingagents

thansoaps.

35. Namethefunctionalgroupspresentinthefollowingcompounds

(a) CH3COCH2CH2CH2CH3


Ans.ketone

(b) CH3CH2CH2COOH

Ans.carboxylicacid

(c) CH3CH2CH2CH2CHO

Ans.aldehyde

(d) CH3CH2OH

Ans.alcohol

36. Howisethenepreparedfromethanol?Givethereactioninvolvedinit.

Ans.Ethanolisheatedat443kinpresenceofexcessofconcentratedsulphuricacidtoobtain

ethene.Thisreactioncanbegivenbyfollowingequation:

37. Intakeofsmallquantityofmethanolcanbelethal.Comment.

Ans.Methanolisoxidizedtomethanalinliver.Methanalcoagulatesthecytoplasmincells;

whichkillsthecells.Methanalalsoactsonopticnervesandcausesblindness.Thus,intakeof

evensmallquantityofmethanalcanbelethal.

38. Agasisevolvedwhenethanolreactswithsodium.Namethegasevolvedandalso

writethebalancedchemicalequationofthereactioninvolved.

Ans.Whenethanolreactswithsodium,thenhydrogengasisevolved.Thisreactioncanbe

givenbyfollowingequation:

39. Etheneisformedwhenethanolat443Kisheatedwithexcessofconcentrated


sulphuricacid.Whatistheroleofsulphuricacidinthisreaction?Writethebalanced

chemicalequationofthisreaction.

Ans.Inthisreaction,sulphuricacidactsasdehydratingagentandalsoascatalyst.

40. Carbon,Group(14)elementinthePeriodicTable,isknowntoformcompoundswith

manyelements.Writeanexampleofacompoundformedwith

(a) chlorine(Group17ofPeriodicTable)

Ans.carbontetrachloride(CCl4)

(b) oxygen(Group16ofPeriodicTable)

Ans.Carbondioxide(CO2)

41. Inelectrondotstructure,thevalenceshellelectronsarerepresentedbycrossesor

dots.

(a) Theatomicnumberofchlorineis17.Writeitselectronicconfiguration

Ans.Electronicconfigurationofchlorine:2,8,7

(b) Drawtheelectrondotstructureofchlorinemolecule.

Ans.Electrondotstructureofchlorinemolecule:


42. Catenationistheabilityofanatomtoformbondswithotheratomsofthesame

element.Itisexhibitedbybothcarbonandsilicon.Comparetheabilityofcatenationof

thetwoelements.Givereasons.

Ans.Bothcarbonandsiliconshowtheabilityofcatenation.Butcompoundsmadebysilicon

arereactiveandlessstable.Ontheotherhand,bondsformedbycarbonareverystrongand

henceorganiccompoundsaremorestablethansiliconcompounds.Itcanbesaidthat

carbonshowsbettercatenationabilitythansilicon.

43. UnsaturatedhydrocarbonscontainmultiplebondsbetweenthetwoC-atomsand

showadditionreactions.Givethetesttodistinguishethanefromethene.

Ans.Saturatedhydrocarbonsgenerallyburnwithacleanflame.Unsaturatedhydrocarbons

burnwithyellowflameandproducelotofsoot.So,whenethaneisburnt,itburnswitha

cleanflameandnosootisproduced.Whenetheneisburnt,itburnswithyellowflameand

produceslotofsoot.

44. MatchthereactionsgiveninColumn(A)withthenamesgivenincolumn(B).

Ans.(a) (iv)

(b) (i)

(c) (ii)

(d) (iii)


45. Writethestructuralformulaeofalltheisomersofhexane.

Ans.


46. Whatistheroleofmetalorreagentswrittenonarrowsinthegivenchemical

reactions?

Ans.catalyst

(b)

Ans.catalyst

(c)

Ans.oxidizingagent


Long Answer Questions

47.Asalt'X'isformedandagasisevolvedwhenethanoicacidreactswithsodium

hydrogencarbonate.Namethesalt'X'andthegasevolved.Describeanactivityand

drawthediagramoftheapparatustoprovethattheevolvedgasistheonewhichyou

havenamed.Also,writechemicalequationofthereactioninvolved.

Ans.Salt'X'issodiumethanoate(CH3COONa)andtheevolvedgasiscarbondioxide(CO2).

Takeatesttubeandtakeethanoicacid(CH3COOH)init.Addsodium

bicarbonate(NaHCO3)totheacid.Closethemouthofthetesttubewithacorkandattacha

deliverytubetoit.Takelimewaterinanothertesttubeandattachthiswiththeotherendof

deliverytube.

Youwillobservethatthelimewaterturnsmilky.Thisshowsthattheevolvedgasiscarbon

dioxide.

Followingreactiontakesplacebetweenethanoicacidandsodiumhydrogencarbonate.


48. (a)Whatarehydrocarbons?Giveexamples.

Ans.Compoundsofhydrogenandcarbonarecalledhydrocarbons,e.g.methane,ethane,

ethene,etc.

(b) Givethestructuraldifferencesbetweensaturatedandunsaturatedhydrocarbonswith

twoexamples,each.

Ans.Allthebondsinsaturatedhydrocarbons(exceptinactiveradicals)aresinglebondsbut

doubleortriplebondispresentinunsaturatedhydrocarbons.

Examplesofsaturatedhydrocarbons:Ethaneandmethane

Examplesofunsaturatedhydrocarbons:Ethyneandethene

(c)Whatisafunctionalgroup?Giveexamplesoffourdifferentfunctionalgroups.

Ans.Functionalgroup–Anatom/groupofatomsjoinedinaspecificmannerwhichis

responsibleforthecharacteristicchemicalpropertiesoftheorganiccompounds.Examples

arehydroxylgroup(–OH),aldehydegroup(–CHO),carboxylicgroup(–COOH)etc.

49. Namethereactionwhichiscommonlyusedintheconversionofvegetableoilsto

fats.Explainthereactioninvolvedindetail.

Ans.Additionreactionisusedintheconversionofvegetableoilstofats.Thisiscalled

hydrogenationofoil.Vegetableoilsgenerallyhavelongchainsofunsaturatedcarbons,while

animalfatshavelongchainsofsaturatedcarbons.

AdditionreactioniscarriedoutinthepresenceofNiasacatalyst.Thisreactioncanbegiven

byfollowingequation:

Itisimportanttonotethatunsaturatedfatishealthyforeating.Butsaturatedfatis

unhealthy.

50. Answerthefollowing:


(a)Writetheformulaanddrawelectrondotstructureofcarbontetrachloride.

Ans.Carbontetrachloride:CCl4.

(b)Whatissaponification?Writethereactioninvolvedinthisprocess.

Ans.Whenestertreatedwithanalkali,thereactiongivesethanolandsodiumethanoate.

Thisreactioniscalledsaponificationreactionbecausethisreactionformsthebasisof

preparationofsoap.Thiscanbegivenbyfollowingequation.

51. Estersaresweet-smellingsubstancesandareusedinmakingperfumes.Suggest

someactivityandthereactioninvolvedforthepreparationofanesterwithwell

labeleddiagram.

Ans.Take1mlethanoland1mlglacialaceticacidinatesttube.Pourafewdropsofconc.

sulphuricacidinthetesttube.

Gentlywarmthetesttubeoverawaterbathforabout5minutes.Afterthat,takeoutthetest

tubeandtransferitscontentsinabeaker.Takethesmellofthecontent.Thesweetsmell


showsthatesterhasbeenmade.Thisreactioncanbegivenbyfollowingequation:

52. Acompound'C'(molecularformula,C2H4O2)reactswithNa–metaltoforma

compound'R'andevolvesagaswhichburnswitha'pop'sound.Compound'C'on

treatmentwithanalcohol'A'inpresenceofanacidformsasweet-smellingcompound

'S'(molecularformula,C3H6O2).OnadditionofNaOHto'C',italsogives'R'andwater.

'S'ontreatmentwithNaOHsolutiongivesback'R'and'A'.IdentifyC,R,A,Sandwrite

downthereactionsinvolved.

Ans.Compound'C'isethanoicacid.Itreactswithsodiumtoformsodiumethanoate.Hence,

compound'R'issodiumethanoateorsodiumacetate.Weknowthathydrogengasburnswith

apopsound.Thisreactioncanbegivenbyfollowingequation:

Whenethanoicacidreactswithmethanolinthepresenceofanacid,weget(methyl

ethanoate)esterwhichisasweet-smellingsubstance.Hence,compoundSismethyl

ethanoateandAismethanol.Thisreactioncanbegivenasfollows:

Whensodiumhydroxideisaddedtoethanoicacid,itgivessodiumethanoateandwater.

WhenmethylethanoateistreatedwithNaOHsolution,itgivesbackmethanolandsodium

ethanoate.

53. LookatFigure4.1andanswerthefollowingquestions


(a)WhatchangewouldyouobserveinthecalciumhydroxidesolutiontakenintubeB?

Ans.CalciumhydroxidesolutioninthetesttubeBbecomesmilky.

(b)WritethereactioninvolvedintesttubesAandBrespectively.

Ans.ReactionintesttubeA:

ReactionintesttubeB:

(c) Ifethanolisgiveninsteadofethanoicacid,wouldyouexpectthesamechange?

Ans.Ethanoldoesnotreactwithsodiumhydrogencarbonate.Hence,samechangecannotbe

observed.

(d) Howcanasolutionoflimewaterbepreparedinthelaboratory?

Ans.Forthis,takedistilledwaterinabeakerandmixcalciumcarbonatepowderinit.After

stirringthoroughly,waittillthemixturesettles.Decanttheclearliquidfromthebeaker.This

liquidislimewater.

54. Howwouldyoubringaboutthefollowingconversions?Nametheprocessandwrite

thereactioninvolved.

(a) ethanoltoethene.


Ans.Ethanolisheatedat443kinthepresenceofexcessofconc.sulphuricacid.This

reactioniscalleddehydrogenation.Thisreactioncanbegivenbyfollowingequation:

(b) propanoltopropanoicacid.

Ans.Propanolistreatedwithalkalinepotassiumpermanganateoracidifiedpotassium

dichromatetoobtainpropanoicacid.

55. DrawthepossibleisomersofthecompoundwithmolecularformulaC3H6Oandalso

givetheirelectrondotstructures.

Ans.Followingaretheisomersofthiscompound.

Propanone

Followingistheelectrondotstructure:


56. Explainthegivenreactionswiththeexamples

(a) Hydrogenationreaction

Ans.Additionofhydrogentounsaturatedhydrocarbontoobtainasaturatedhydrocarbonis

calledhydrogenationreaction.Hydrogenationisusedforconvertingunsaturatedvegetable

oilintofat.Thiscanbeshownbyfollowingequation:

(b) Oxidationreaction

Ans.Whenoxygenisaddedtoalcoholtomakecarboxylicacid,thisiscalledoxidation

reaction.Followingisanexampleofoxidationofalcohol.

(c) Substitutionreaction

Ans.Saturatedhydrocarbonsarefairlyunreactive.Butinthepresenceofsunlight,chlorine

substituteshydrogenonebyone.

(inthepresenceofsunlight)

Thissubstitutioncangoontill,carbontetrachlorideisobtained.

(d) Saponificationreaction

Ans.Whenesteristreatedwithanalkali,thereactiongivesethanolandsodiumethanoate.

Thisreactioniscalledsaponificationreactionbecausethisreactionformsthebasisof


preparationofsoap.Thiscanbegivenbyfollowingequation.

(e) Combustionreaction

Ans.Whenasubstanceburnsinthepresenceofoxygen,thereactioniscalledcombustion.

Followingisanexampleofcombustionreaction.

57. AnorganiccompoundAonheatingwithconcentratedH2SO4formsacompoundB

whichonadditionofonemoleofhydrogeninpresenceofNiformsacompoundC.One

moleofcompoundConcombustionformstwomolesofCO2and3molesofH2O.

IdentifythecompoundsA,BandCandwritethechemicalequationsofthereactions

involved.

Ans.CompoundAisethanol.Whenitisheatedwithconcentratedsulphuricacid,weget

ethene.So,compoundBisethene.Thiscanbeshownbyfollowingequation.

Whenetheneisheatedinthepresenceofnickel,wegetethane.Thiscanbeshownby

followingequation.

(CompoundC)

When1moleofethaneisburnt,weget2molesofcarbondioxideand3molesofwater;as

shownbyfollowingequation.


exercise multiple choice questions(mcqs) · 2020. 9. 15. · chapter 4 carbon and its compounds...

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