lakshya study point 3.pdfmaterial downloaded from mycbseguide.com. 3 / 26 80 50 table b (blood...
TRANSCRIPT
MaterialdownloadedfrommyCBSEguide.com. 1/26
CBSEClass10Science
SamplePaper03(2019-20)
MaximumMarks:80
TimeAllowed:3hours
GeneralInstructions:
i. Thequestionpapercomprisesthreesections–A,BandC.Attemptallthesections.
ii. Allquestionsarecompulsory.
iii. Internalchoiceisgivenineachsection.
iv. AllquestionsinSectionAareone-markquestionscomprisingMCQ,VSAtypeand
assertion-reasontypequestions.Theyaretobeansweredinonewordorinonesentence.
v. AllquestionsinSectionBarethree-mark,short-answertypequestions.Thesearetobe
answeredinabout50-60wordseach.
vi. AllquestionsinSectionCarefive-mark,long-answertypequestions.Thesearetobe
answeredinabout80–90wordseach.
vii. Thisquestionpaperconsistsofatotalof30questions.
SectionA
1. Statethelawofconservationofmass.
2. Accountforthefollowing:Elementsofgroup18arecalledzerovalent.
3. Answerthequestionsthatfollowsonthebasisofyourunderstandingofthe
followingparagraphandtherelatedstudiedconcepts:
Bio-gasisanexcellentfuelasitcontainsupto75%methane.Itburnswithoutsmoke,
leavesnoresiduelikeashinwood,charcoalandcoalburning.Itisheatingcapacityis
high.Bio-gasisalsousedforlighting.Theslurryleftbehindisremovedperiodically
andusedasexcellentmanure,richinnitrogenandphosphorous.Thelarge-scale
utilisationofbio-wasteandsewagematerialprovidesasafeandefficientmethodof
LAKSHYA STUDY POINT
MaterialdownloadedfrommyCBSEguide.com. 2/26
waste-disposalbesidessupplyingenergyandmanure.
i. Whattypeofsourceofenergyismentionedintheabovepicture?
ii. Doesthissourceofenergycancausepollution?Justifyyouranswerwithabrief
explanation.
iii. Writethetwoadvantagesofbiogasasfuel.
iv. WritethedifferentcomponentsofBiogas?
4. Followingquestionsarebasedonthetwotablesgivenbelow.Studythesetables
relatedtobloodsugarlevelsandanswerthequestionsthatfollow.
TableA(Bloodglucosechart)
MeanBloodGlucoseLevel(mg/dL)
Doctor'sadviceneeded 380
350
315
280
250
215
Good 180
150
Excellent 115
MaterialdownloadedfrommyCBSEguide.com. 3/26
80
50
TableB(BloodReportofPatientXandY)
Timeofcheck BloodGlucoseranges(mg/dL)
PatientX PatientY
Beforebreakfast(Fasting) <100 70-130
Beforelunch,supperandsnack <110 70-130
Twohoursaftermeals <140 <180
Bedtime <120 90-15
Answerthefollowingquestions:
a. RefertoTableBshowingthebloodreportofthelevelsofglucoseofpatientsXand
Y.Inferthediseasewhichcanbediagnosedfromthegivendata.
b. Identifythehormonewhoselevelinthebloodisresponsiblefortheabovedisease.
c. Whichoneofthefollowingdietswouldyourecommendtotheaffectedpatient?
i. Highsugarandalow-fatdiet.
ii. Lowsugarandhighproteindiet.
iii. HighFatandlowfibrediet.
iv. Lowsugarandhighfibrediet.
d. RefertoTableAandsuggestthevalueofthemeanbloodglucoselevelbeyond
whichdoctor’sadviceisnecessary:
i. 80mg/dL
ii. 115mg/dL
iii. 50mg/dL
iv. 80mg/dL
5. ThecauseofAstigmatismis
a. Varyingcurvatureinverticallines
b. Varyingcurvatureinhorizontallines
MaterialdownloadedfrommyCBSEguide.com. 4/26
c. Varyingcurvatureinbothhorizontalandverticallines
d. Noneofthese
OR
StatementA:Thefocallengthoftheeyelensisfixed,StatementB:Thecorneaofthe
eyecanbecomparedwiththeshutterofthecamera
a. NeitherstatementAnorstatementBistrue
b. BoththeStatementAandBaretrue
c. StatementBistrue,Aisfalse
d. StatementAistrue,Bisfalse
6. HowmanyNationalParksarethereinGujarat?
a. 5
b. 30
c. 24
d. 4
7. Whichoffollowingstatementisnotcorrectaboutelectricfuse
A.Itisalwaysconnectedinlivewire
B.Itisalwaysconnectedintheendofthecircuit
C.Thinnerthefusewire,greaterisitscurrentcapacity
D.Itscurrentcapacitymustbelessthanthemaximumcurrent
a. BandC
b. AandB
c. AandC
d. A,B,CandD
8. Bleachingpowderisusedinthepaperindustryasa
a. dehydratingagent
MaterialdownloadedfrommyCBSEguide.com. 5/26
b. bleachingagent
c. reducingagent
d. dryingagent
OR
Anacidcanreactwith
a. PbSO4
b. AgCl
c. Na2SO4
d. Na2CO3
9. Matchthefollowingwiththecorrectresponse:
(1)Saprotrophs (A)Organismsobtainingfoodfromgreenplants
(2)Parasites (B)Organismsobtainingfoodfromhost
(3)Autotrophs (C)Organismsobtainingfoodfromdeadplantsandanimals
(4)Herbivores (D)Organismswhichpreparetheirownfood
a. 1-B,2-D,3-A,4-C
b. 1-C,2-B,3-D,4-A
c. 1-D,2-A,3-C,4-B
d. 1-A,2-C,3-B,4-D
10. Innaturalecosystems,decomposersinclude:
a. Onlybacteriaandfungi
b. Herbivoresandcarnivores
MaterialdownloadedfrommyCBSEguide.com. 6/26
c. Onlymicroscopicanimals
d. Both(b)and(c)
11. Electropositivecharacterofelementsinaperiod___________fromlefttoright.
a. Increases
b. firstincrease,thendecrease
c. remainsthesame
d. decreases
12. AqueoussolutionsofzincsulphateandironsulphateweretakenintesttubesIandII
byfourstudentsA,B,CandD.Metalpiecesofironandzincweredroppedinthetwo
solutionsandobservationsmadeafterseveralhourswererecordedintheformof
tableasgivenbelow:
Thecorrectreportinghasbeenmadeinobservations:
a. A
b. C
c. D
d. B
13. Assertion:Inesterification,carboxylicacidandalcoholreactinthepresenceofacid
togiveester.
MaterialdownloadedfrommyCBSEguide.com. 7/26
Reason:Esterificationisthereverseofsaponification.
a. AssertionisCORRECTbut,reasonisINCORRECT.
b. AssertionisINCORRECTbut,reasonisCORRECT.
c. BothassertionandreasonareCORRECTandreasonistheCORRECTexplanationof
theassertion.
d. BothassertionandreasonareCORRECTbut,reasonisNOTTHECORRECT
explanationoftheassertion.
14. Assertion:Whenthelengthofawireisdoubled,thenitsresistancealsogetsdoubled.
Reason:Theresistanceofawireisdirectlyproportionaltoitslength.
a. AssertionisINCORRECTbut,reasonisCORRECT.
b. BothassertionandreasonareCORRECTandreasonistheCORRECTexplanationof
theassertion.
c. BothassertionandreasonareCORRECTbut,reasonisNOTTHECORRECT
explanationoftheassertion.
d. AssertionisCORRECTbut,reasonisINCORRECT.
SectionB
15. (a)AnaqueoussolutionhasaPHvalueof7.0.Isthissolutionacidic,basicorneutral?
(b)IfH+concentrationofasolutionis molL-1whatwillbeitsP4value?
(c)WhichhashigherPHvalue:1-MHClor1-MNaOH
16. Givethecharacteristictestsfor .
OR
Zincpieceswereplacedineachofthefourtesttubescontainingdifferentsalt
solutionsasshownbelow
:
Acolourchangewouldbeobservedinsolutions:
17. ThepositionofthreeelementsA,BandCinthePeriodicTableareshownbelow:
MaterialdownloadedfrommyCBSEguide.com. 8/26
Group16 Group17
- -
- A
- -
B C
i. StatewhetherAisametalornon-metal.
ii. StatewhetherCismorereactivethanA
iii. WillCbelargerorsmallerinsizethanB?
iv. Whichtypeofion,cationoranion,willbeformedbyelementA?
18. Whatismeantbyclottingofblood?Writeaflowchartshowingmajoreventstaking
placeinclottingofblood?
OR
Whatistheadvantageofdigestivecavity?
19. Whydoesthesunappearreddishinthemorning(aswellasinevening)?
20. Whatarefossils?Whatdotheytellusabouttheprocessofevolution?
21. Listintabularformthreedistinguishingfeaturesbetweencerebrumandcerebellum.
22. i. Thediagramshowsabarmagnetsurroundedbyfourplottingcompasses.Copy
thediagramandmarkthedirectionofthecompassneedleforeachofthecasesB,
CandD.
ii. WhichistheNorthpole,XorY?
23. Supposeyourparentshaveconstructedatworoomhouseandyouwantthatinthe
livingroomthereshouldbeaprovisionofoneelectricbulb,oneelectricfan,a
refrigeratorandaplugpointforappliancesofpowerupto2kilowatts.Drawacircuit
diagramshowingelectricfuseandearthingassafetydevices.
MaterialdownloadedfrommyCBSEguide.com. 9/26
24. Inthefiguregivenbelow,anarrowbeamofwhitelightisshowntopassthrougha
triangularglassprism.Afterpassingthroughtheprism,itproducesaspectrumXYon
thescreen.
i. Namethephenomenon.
ii. StatethecoloursseenatXandY.
iii. Whydodifferentcoloursofwhitelightbendatdifferentanglesthroughaprism?
OR
Sudhafindsoutthatthesharpimageofwindowpaneofhersciencelaboratoryis
formedatadistanceof15cmfromthelens.Shenowtriestofocusthebuildingvisible
ofheroutsidethewindowinsteadofthewindowpanewithoutdisturbingthelens.In
whichdirectionwillshemovethescreentoobtainasharpimageofthebuilding?
Whatistheapproximatefocallengthofthislens?
SectionC
25. Howwillyougetmetalfromconcentratedore?
26. a. Namethegasevolvedduringfermentationprocess.
b. Whatroleisplayedbyyeastintheconversionofcanesugar(C12H22O11)to
ethanol?
c. Howcanthefollowingbeobtainedfrompureethanol?Expresschemicalreactions
bythechemicalequations.
i. Sodiumethoxide
ii. Ethylethanoate
iii. Ethanal
27. Whatisthedifferencebetweenanintercellularandintracellulardigestion?
MaterialdownloadedfrommyCBSEguide.com. 10/26
28. Whyarebudding,fragmentationandregenerationallconsideredasasexualtypesof
reproduction?WithneatdiagramsexplaintheprocessofregenerationinPlanaria.
OR
Givereasons:
i. Placentaisextremelyessentialforfoetaldevelopment.
ii. Blockingofvasdeferenspreventspregnancy.
iii. Windactsasapollinatingagent.
iv. Useofcondomspreventspregnancy.
v. BlockingofFallopiantubespreventspregnancy.
29. Whatistheneedofcombiningdifferentresistors?Whatistheresultantresistance
whenanumberofresistancesareconnectedinseries?
30. Anairbubbleinwaterisshowninthefigure.Threeraysoflightareincidentonthe
airbubble.
Theangleofincidenceofray1ontheairbubbleisgreaterthanthecriticalangle.The
angleofincidenceofray2ontheairbubbleislessthanthecriticalangle.Ray3is
perpendiculartothesurfaceofthebubble.
i. Infigureatthepointwhereray1meetstheairbubble,mark
a. thenormaltothesurface
b. theangleofincidence
ii. Completetheraydiagramtoshowhowallthreerayscontinueaftertheymeetthe
airbubble.
iii. Definerefractiveindexofwater.Ifthespeedoflightinairis3 108ms-1andthe
speedoflightinwateris2.2 108ms-1.Calculatetherefractiveindexofwater.
OR
MaterialdownloadedfrommyCBSEguide.com. 11/26
Anairbubbleinwaterisshowninthefigure.Threeraysoflightareincidentonthe
airbubble.
Theangleofincidenceofray1ontheairbubbleisgreaterthanthecriticalangle.The
angleofincidenceofray2ontheairbubbleislessthanthecriticalangle.Ray3is
perpendiculartothesurfaceofthebubble.
i. Infigureatthepointwhereray1meetstheairbubble,mark
a. thenormaltothesurface
b. theangleofincidence
ii. Completetheraydiagramtoshowhowallthreerayscontinueaftertheymeetthe
airbubble.
iii. Definerefractiveindexofwater.Ifthespeedoflightinairis3 108ms-1andthe
speedoflightinwateris2.2 108ms-1.Calculatetherefractiveindexofwater.
MaterialdownloadedfrommyCBSEguide.com. 12/26
CBSEClass10Science
SamplePaper03(2019-20)
Answer
SectionA
1. Massisneverlostorgainedinchemicalreactions.Wesaythatmassisalways
conserved.Inotherwords,thetotalmassofproductsattheendofthereactionis
equaltothetotalmassofthereactantsatthebeginning.
2. Elementsofgroup18havecompletelyfilledoutermostshellandhavenotendencyto
gainorloseelectrons.Thus,elementsofthisgrouphavezerovalencyandarealmost
unreactive.So,theyarecalledzerovalent.
3. i. Itisarenewablesourceofenergy.
ii. No,Biogasisarenewable,aswellasaclean,sourceofenergy.Thegasgenerated
throughbio-digestionisnon-polluting;itactuallyreducesgreenhouseemissions.
iii. Thetwoadvantageofbiogasasafuelare:
a. Itburnswithoutsmoke,leavesnoresiduelikeashinwood,charcoalandcoal
burning.
b. Eco-friendly,cheaper,easytouse.
iv. Biogasisamixtureofmethane,hydrogen,carbondioxide,andhydrogensulphide.
4. a. Diabetes
b. (b)Insulin
c. (iv)lowsugarhighfibrediet
d. (i)180mg/dL
5. (c)Varyingcurvatureinbothhorizontalandverticallines
Explanation:Thedefectbywhichthepersonisnotabletodifferentiatehorizontal
andverticalposition,iscalledastigmatism.Itiscausedbyanerrorintheshapeofthe
cornea.Itcanbecorrectedbyusingcylindricallenses.
OR
(a)NeitherstatementAnorstatementBistrue,Explanation:Theimageontheretina
isformedbytwolenses–thecornea,whichisaconverginglenswhosefocallengthis
MaterialdownloadedfrommyCBSEguide.com. 13/26
fixed,andtheeye-lens,whichisaconvexlenswhosefocallengthisnotfixedandcan
bevariedbychangingitsshape.
Inoptics,anapertureisaholeoranopeningthroughwhichlighttravels.Thepupilof
theeyeisitsapertureinopticsnomenclature;theirisisthediaphragmthatservesasthe
aperturestop.
6. (d)4,Explanation:TheGujaratstateofwesternIndiahasfourNationalParksand
twenty-oneWildlifeSanctuarieswhicharemanagedbytheForestDepartmentofthe
GovernmentofGujarat.
S.No.Nameof
NationalPark
Yearof
NotificationTotalArea(km²)
1 VansdaNationalPark 1979 23.99
2 BlackbuckNationalParkVelavadar 1976 34.53
3 GirForestNationalPark 1975 258.71
4 MarineNationalPark,GulfofKutch 1982 162.89
7. (a)BandCExplanation:
A.Afusewireisasafetywireconnectedinserieswiththelivewire,incaseofany
largecurrentsupplyormalfunctioningintheelectricconnectionsitmeltsandbreaks
theelectriccircuit.
B.Afusewireisconnectedinseriessoastopassthecurrenttotallythroughthefuse.
Itisnotconnectedintheendofthecircuit.
C.Therelationbetweenthicknessofawireandit'scurrentcarryingcapabilityisthat,
morethethicknessmorethecurrentawirecancarry.Sofusewiresaremadeof
sufficientthickness.Meansthinnerthefusewire,lesserisitscurrentcapacity.
D.Thefuseneedstoberatedslightlyhigherthanthemaximumoperatingcurrentof
theprotecteddevice,sothatthefusewon'tblowwhentheequipmentisused.
StatementBandCarenotcorrectaboutelectricfuse.
8. (b)bleachingagent,Explanation:Bleachingpowderisusedtobleachcottonand
linenintextileindustryandwoodpulpinpaperindustry.
OR
MaterialdownloadedfrommyCBSEguide.com. 14/26
(d)Na2CO3,Explanation:AcidsreactwithmetalcarbonatestoevolveCO2gas.
9. (b)1-C,2-B,3-D,4-A,Explanation:Organismscanbegroupedasproducers,
consumersanddecomposersaccordingtothemannerinwhichtheyobtaintheir
sustenancefromtheenvironment.Producersorautotrophspreparetheirown
food.Consumerscanbeclassedasherbivores,carnivores,omnivoresand
parasites.Herbivoresobtainfooddirectlyfromgreenplants.Parasitesobtainfood
fromahost.
(1)Saprotrophs (C)Organismsobtainingfoodfromdeadplantsandanimals
(2)Parasites (B)Organismsobtainingfoodfromhost
(3)Autotrophs (D)Organismswhichpreparetheirownfood
(4)Herbivores (A)Organismsobtainingfoodfromgreenplants
10. (a)Onlybacteriaandfungi,Explanation:Innaturalecosystems,decomposers
includemicroorganisms,comprisingbacteriaandfungi,whichbreakdownthedeadremains
andwasteproductsoforganisms.Thesedecomposersbreakdownthecomplexorganic
substancesintosimpleinorganicsubstances.
11. (d)decreases,Explanation:Aswemovefromlefttorightinaperiod,thepositive
chargeincreasesduetogradualincreaseinthenumberofprotons.So,thevalence
electronsarepulledinmorestronglybythenucleusanditbecomesmoreandmore
difficultfortheatomstoloseelectrons.Thus,onmovingfromlefttorightinaperiod,
thetendencyofatomstoloseelectronsdecreasesi.eelectropositivecharacterof
elementsdecreases.
12. (b)C,Explanation:Fe+ZnSO4→NoreactionItisbecauseironislessreactivethanZinc.
Zn+FeSO4→ZnSO4+Fe
Thesolutionbecomescolourlessandblackirongetsdeposited.
13. (a)AssertionisCORRECTbut,reasonisINCORRECT.Explanation:Assertionis
CORRECTbut,reasonisINCORRECT.
14. (b)BothassertionandreasonareCORRECTandreasonistheCORRECTexplanationof
theassertion.Explanation:BothassertionandreasonareCORRECTandreasonisthe
CORRECTexplanationoftheassertion.
SectionB
MaterialdownloadedfrommyCBSEguide.com. 15/26
15. (a)Thesolutionisneutralisnature.
(b)[H+]=
=10-2M
PH=
=-log[H+]
=-log[10-2]
=-(-2)log10=2
(c)1MNaOHsolution(basic)higherPH.Value
1MHClsolution(acidic)lowerPH.Value
16. Carbondioxide( )gasturnslimewatermilkywhenpassedthroughitduetothe
formationofinsolublecalciumcarbonate.
OR
ThecolourchangewilltakeplaceinIIIandIVaszincismorereactivethanironas
wellascopper.
17. i. Aisanon-metal.
ii. CislessreactivethanA.
iii. CwillbesmallerthanB.
iv. Awillformanion.
18. Abloodclotisformedwhenbloodcellsandfibrinstrandsclumptogether.Aclotthatblocksbloodflowiscalledathrombus.
MaterialdownloadedfrommyCBSEguide.com. 16/26
OR
Adigestivecavitynotonlyisaplacewheredigestionoflargeparticlescantakeplace,
butitcanalsobeusedtostorefood.
MaterialdownloadedfrommyCBSEguide.com. 17/26
19. Earthissurroundedbyenvelopeofgasescalledatmosphere.Atthetimeofsunrise(or
atsunset),lighthastotravelgreaterthickness[ABatsun-riseandBCatsunset]than
whatitcoverswhensunisoverheadatnoon[ithastotravelonlyDB].The
wavelengthofbluecolourisabouthalfthatofred,bluelightisscatterednearly=16
timesred.Asaresult,thesunappearsredatsunriseoratsunsetduetonegligible
scatteringofredincomparisonwithblue.
20. Preservedtracesoflivingorganismsarecalledfossilsfoundclosertothesurfaceof
eartharemorerecentinoriginthanthefossilswefindindeeperlayers.
Fossilsalsohelpustofindevolutionaryrelationbetweenorganisms.
21.
Cerebrum Cerebellum
1.Itisapartoftheforebrain. 1.Itisapartofthehindbrain.
2.Itformabout83%partofthetotal
brainweight.
2.Itformabout11%partofthetotal
brainweight.
3.Itisthelargestpartofthebrain.3.Itisthesecond-largestpartofthe
brain.
22. i.
ii. TheNorthPoleisX.
23. Thecircuitdiagramshowingtheelectricfuseandearthingassafetydevicesisas
MaterialdownloadedfrommyCBSEguide.com. 18/26
follows:
24. i. Thephenomenoniscalleddispersion.
ii. X—VioletY—Red
iii. Differentcoloursofwhitelightbendthroughdifferentangleswithrespecttothe
incidentbeamoflightduetodifferenceinspeedoflightofdifferentwavelengths.
OR
LetusassumethatthewindowpaneisbetweenF2andinfinityfromthislensandthis
isaconvexlens.WeknowthatwhentheobjectisbetweeninfinityandF2,itsinverted
andrealimagesisformedbetween2Fand2F2.
Now,thedistantbuildingisatinfinityfromthelens.Itsimagewouldbeformedat2F.
So,thescreenneedstobemovedtowardsthelensinordertogetasharpimage.Its
approximatefocallengthis10cm(lessthanimagedistanceinearliercase).
SectionC
25. Extractionofthemetalfromtheconcentratedore.Themetalisextractedfromthe
concentratedorebythefollowingsteps:
(i)Conversionoftheconcentratedoreintoitsoxide.Thisisusuallydoneby
calcinationandroastingprocess.Themethoddependsuponthenatureoftheore.A
carbonateoreisconvertedintooxidebycalcinationwhileasulphideoreisconverted
intooxidebyroasting.
(ii)Conversionofoxidetometalbyreductionprocess.
(i)Conversionoforeintometaloxide:Itcanbedonebytwomethods
(a)Calcination:Itistheprocessofheatingtheconcentratedoreintheabsenceofair.
Thecalcinationprocessisusedtoremovedvolatileimpurities,waterfromthe
MaterialdownloadedfrommyCBSEguide.com. 19/26
hydratedoresandtoconvertcarbonateoresintometaloxide.
Forexample:
(i)Zincoccursaszinccarbonateincalamine(ZnCO3).Theoreiscalcinated(heated
strongly)intheabsenceofairtoconvertittozincoxide.Duringcalcination,carbon
dioxideisexpelled.
ZnCO3 ZnO + CO2
Zinccarbonate(Calamineore) (Zinc.Oxide)
(ii)AluminiumoccursasAl2O3.2H2Oinitsbauxiteore.Whenthebauxiteoreis
calcined,watervapoursareexpelledandanhydrousaluminiumoxideisobtained.
Al2O3.2H2O Al2O3 + 2H2O
BauxiteOre AluminiumOxide
b)Roasting:Itistheprocessofheatingtheconcentratedorestronglyinthepresence
ofexcessair.Thisprocessisusedforconvertingsulphideorestometaloxide.
Forexample,zincoccursassulphideinzincblende(ZnS).Itisstronglyheatedin
excessofairwhenitformszincoxideandsulphurdioxidegasisexpelled.
2ZnS+3O2 2ZnO + 2SO2
Zincsulphide(Zincblendeore) ZincOxide
ii)Conversionofmetaloxidetometal:Themetaloxideformedaftercalcinationor
roastingisconvertedintometalbyreduction.Someofthemethodscommonlyused
forthereductionofmetaloxidestometalsarediscussedbelow:
I)Reductionbyheatingintheair:Metalslowinthereactivityseriescanbe
obtainedfromtheiroxidesbyheatinginair.Forexample,mercuryisobtainedfrom
cinnabar(HgS)orebythismethod.Themethodinvolvesthefollowingsteps:
i)Theconcentratedmercuricsulphide(cinnabaror)isroastedinairwhenmercuric
oxideisformed.
MaterialdownloadedfrommyCBSEguide.com. 20/26
2HgS + 3O2 2HgO + 2SO2
Mercuricsulphide(Cinnabarore) Mercuricoxide
2HgO → 2Hg + O2
Mercuricoxide Mercuricmetal
ii)Mercuricoxideisheatedtoabout300oCanditdecomposestogivemercurymetal.
II)Chemicalreduction:Themetaloxidesfromcalcinationorroastingprocessesare
reducedtofreemetalbyusingchemicalagentslikecarbon,aluminium,sodiumor
calcium.
(a)Reductionwithcarbon:Theoxidesofmoderatelyreactivemetalslikezinc,
copper,nickle,tin,leadetc.canbereducedbyusingcarbonasreducingagent.Inthis
process,themetaloxideismixedwithcokeandheatedinafurnace.Carbonreduces
themetaloxidetofreemetal.
Fore.g.whenzincoxideisheatedwithcarbon,zincmetalisproduced.
ZnO + C Zn + CO
Zincoxide Reducingagent Zincmetal Carbonmonoxide
Similarly,leadisobtainedfromleadoxidebyheatingwithcarbon.
PbO + C → Pb + CO
Leadoxide Leadmetall
Cokeisverycommonlyusedasareducingagentbecauseitischeap.
(b)Reductionwithcarbonmonoxide:Metalscanbeobtainedfromoxidesby
reductionwithcarbonmonoxideinthefurnace.Forexample,ironisobtainedfrom
ferricoxidebyheatingwithcarbonmonoxide.
Fe2O3(s)+3CO 2Fe+3CO2
c)Reductionwithaluminium:Certainmetaloxidesarereducedbyaluminiumto
metals.Themethodisknownasaluminothermyorthermiteprocess.Forexample,
chromium,manganese,titanium,vanadiummetalsareobtainedbythereductionof
MaterialdownloadedfrommyCBSEguide.com. 21/26
theiroxideswithaluminiumpowder.
3MnO2 + 4Al 3Mn + 2Al2O3
Manganeseoxide Manganese
Cr2O3 + 2Al 2Cr + Al2O3
Chromiumoxide Chromium
Similarly,chromiumisobtainedbyheatingchromiumoxidewithaluminium
powder.
(d)Reductionbyelectrolysisorelectrolyticreduction:Theoxidesofactivemetals
arecommonlyextractedbytheelectrolysisoftheirfusedsaltsusingsuitable
electrodes.Thisisalsocalledelectrolyticreduction.Theprocessofextractionof
metalsbyelectrolysisprocessiscalledelectrometallurgy.
Fore.g.,aluminiumoxideisverystableandaluminiumcannotbepreparedby
reductionwithcarbon.Itispreparedbytheelectrolysisofmoltenalumina(Al2O3).In
thisprocess,purealuminaisdissolvedinmoltencryolite(Na3ALF6)inanirontank
linedwithcarbon.Duringelectrolysis,thealuminiumions,Al3+arereducedat
cathode(bytheelectrons)toformaluminium.
Al3+ + 3e- → Al
Aluminiumion(frommoltenalumina) Aluminium(Atcathode)
Duringelectrolyticreductionofmoltensalts,themetalsarealwaysproducedatthe
cathode(negativeelectrode).
26. a. Thegasthatisevolvedisevolvedduringthefermentationprocessiscarbon
dioxide(CO2).Itisaccompaniedbybriskeffervescence.
b. Yeastisthesourceofenzymes-invertaseandzymase.Theseenzymesareneeded
forfermentationofcanesugar(C12H22O11)toethanol.
Invertasehelpsinbreakingsucrose(anaturallyoccurringcarbohydratepresent
incanesugar)intoitscomponents-glucoseandfructose.
MaterialdownloadedfrommyCBSEguide.com. 22/26
Zymaseconvertsglucoseintoalcoholandcarbondioxide.
c. Therequiredchemicalreactionsforpureethanolareasfollows:-
i. Sodiumethoxide( )canbeobtainedfrompureethanolwhenitis
madetoreactwithsodium.Sodiumdisplaceshydrogenfromethanol.
ii. Ethylethanoatecanbeobtainedfrompureethanolbywarmingethanolwith
ethanoicacidinthepresenceofconc.sulphuricacid.Thisisesterification
reaction.
C2H5OH+CH3COOH +H2O
iii. Ethanalcanbeobtainedbyperformingthepartialoxidationofpureethanolin
theabsenceofwater.Achromiumbasedreagentsuchaschromiumtrioxide
canbeused.
C2H5OH+ O2 CH3CHO+H2O
27.
Intracellulardigestion Extracellulardigestion
1)Thedigestionoffoodoccurswithinthe
cell.
1)Thedigestionoccursinthecavityof
alimentarycanal.
2)Digestiveenzymesaresecretedbythe
surroundingcytoplasmintothefood
vacuole.
2)Digestiveenzymesaresecretedby
specialcellsintothecavityofalimentary
canal.
3)Digestiveproductsarediffusedintothe
cytoplasm.
3)Digestiveproductsdiffuseacrossthe
intestinalwallintovariouspartsofthe
body.
4)Itisalessefficientmethod.4)Itisamoreefficientmethodof
digestion.
5)Itoccursinunicellularorganisms. 5)Itoccursinmulticellularorganisms.
28. Budding,fragmentationandregenerationareallexampleofasexualreproduction
becausealloftheminvolveonlyoneparent.Maleandfemalegametesarenot
MaterialdownloadedfrommyCBSEguide.com. 23/26
involvedinthereproduction.Thusinallofthethreeprocessnovariationis
produced.
Planariacanbecutintoanynumberofpiecesandeachpiecegrowsintoacomplete
organism.Thisprocessisknownasregeneration(seefig.)Regenerationiscarriedout
byspecialisedcellsknownasneoblast(adultstemcells).
Thesecellsproliferateandproducelargenumbersofcells.Fromthismassofcells,
differentcellsundergochangestobecomevariouscelltypesandtissues,givingriseto
wholeneworganismwithsameDNAcontentasitsparent.Thesechangestakeplace
inanorganisedmannerreferredtoasdevelopment.
OR
i. Placentaisatemporaryorganwhichisextremelyessentialforfoetaldevelopment
becauseithelpsinnutrition,respiration,excretion,etc.,ofthefoetusthroughthe
maternalsupply.Babyconnectswithplacentaviaumblicalcord.
ii. Blockingofvasdeferensisknownasvasectomywhichpreventspassageof
sperms,hence,thereisnofertilisationthusitpreventspregnancy.
iii. Anemophilyorwindpollinationisaformofpollinationwhere,windactsasa
pollinatingagentbecauseithelpsintransferofpollengrainsfromantherto
stigmaofaflower.e.g.wheat,ricecorn.
MaterialdownloadedfrommyCBSEguide.com. 24/26
iv. Condomsasphysicalbarrier,whichprevententryofspermsintovagina,hence
preventspregnancy.
v. IfFallopiantubeisblockedsurgically,whichisbetterknownbythename
tubectomy,spermandeggdonotmeetandfuseandfertilisationdoesnottake
place.
29. Combinationofresistors:Resistorsofallvaluesofresistancesarenotavailable.Hence
resistorsareconnectedinanumberofwaystoincreaseordecreasethecombined
resistance.Therearetwodistinctwaysinwhichresistorscanbeconnected.Theyare
resistorsinseriesandresistorsinparallel.
Resistorsconnectedinseries
Resistorsaresaidtobeinseriesiftheyarejoinedendtoendsothatthesamecurrent
flowsthrougheachoneoftheminsuccession.Sincethereisasinglepathforthe
movingcharge,thesamecurrentmustflowthrougheachresistor.Lettheconductor
AB,BCandCDhavingresistancesequaltoR1,R2andR3respectively,bejoinedin
seriesandletthecurrentpassingthroughthembeI.
LetV1,V2andV3bethepotentialdifferencebetweentheendsofthefirst,secondand
thirdconductorrespectively.
ByOhm'slaw,
V1=IR1;V2=IR2andV3=IR3
IfVisthetotalpotentialdifferencebetweentheendsAandDandRsistheeffective
resistanceofthecombinationofalltheresistors,then
V=IRsButV=V1+V2+V3
ORIRs=IR1+IR2+IR3
ORRs=R1+R2+R3
Theaboveresultholdsgoodforanynumberofresistorsjoinedinseries.
MaterialdownloadedfrommyCBSEguide.com. 25/26
Thuswhensomeresistorsarejoinedinseries,thetotalresistanceisthesumof
individualresistances.
30. i. Diagramforfirstpartisshownas:
ii. Thethreerayscontinueaftertheymeettheairbubbleareshownas:
iii. Refractiveindexofwaterisdefinedastheratioofthespeedoflightinavacuum
tothespeedoflightinwater.
Speedoflightinair, ms-1
Speedoflightinwater, ms-1
Therefore,Refractiveindex,
=1.4
OR
MaterialdownloadedfrommyCBSEguide.com. 26/26
i. Diagramforfirstpartisshownas:
ii. Thethreerayscontinueaftertheymeettheairbubbleareshownas:
iii. Refractiveindexofwaterisdefinedastheratioofthespeedoflightinavacuum
tothespeedoflightinwater.
Speedoflightinair, ms-1
Speedoflightinwater, ms-1
Therefore,Refractiveindex,
=1.4