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ISC Class XII Prelims 2025 : Chemistry (St. Augustines Day School, Kolkata)

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Subhadip Mukherjee
St. Augustine's Day School, Kolkata

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Page 1 of 7 ST.A UGUST I NE'S DAY SCHOOL. BARRACl<PORE SESSION: 2025 - 2026 PRE-SELECTION EXAMINATION SUB: CHEMJSTRY FULL MARKS: 70 CLASS : :\.'11 TfME : 3 ROURS (Candidates are allowed additional I 5 minutes for only reading the paper. They must NOT star/ writing during this time) , ___________ 77iis paper is divided into f our sections - A, B, C and D Answer al/ q11e.~tio11s. Section A c:om;ists oJone qth!Stion ilavlng su b-parts of one m ark each. Section -B consist.1 v/'te,r questions a/two marks each. Sectio11 - C consists ofseve,r questions ofthree marks euch. and Sectio,r - D consisl!; o,(three questions ofj.1ve marks each J.uremal choices have been provided in oue question each i11 Section 8, C and Section D. All wurking, including rough work, should he done 0111he same sheet as and adjacem rn the rest of the answer. The imended marks fo r q11es1io11s or parts of questions are given in hraclrets / J Baltmced equations 11111st be given wheren'r possihle and diugrams 11 here they are hel(l/11/ When sn/ving 11u111eric:al prohlems, al/ e\'senlia/ working m11s1 be 1 hown. /11 worki11g u111prohli:111.1. 11se the jiJl/011 i11x dut" Gus L'On:. lu111 /( = / l utm I . YH7 cal dc1:; 1 1110/ 1 J,/111 ; '1fm H. J I -I .JK 1 mo/ /01 .J.I. A 11vg111/m .1 J/11111b, r 1 0. 081 elm ; atm K 1/.'uruJuy - IJ65IJO co11/ombt 6 0;;3 :< I fJ ' 1 1 110/ Page 2 c' 7 SECTT0., - A (14 .MA.RKSI Qaesno-n-1 (..t. 1 Fi.I JJ IM b ~ b:, choosmg the appropriate word(s) from those given in the 141 ~..:.e-..s (Lv., =.en.. CH;0H. - 3 septic C:Hd fire nimguishe CH.I Lu.. le ss, positive. an1isep1k. C:HsOH. - .2,.~e lirdi~ l Ci)\1~ e-...:.ane oc heat.ng "itt 1 .om H' gj,es < '1 ~ and ,,. .,, ' fri)Tbt ,r : Hoff facto- of ~ it acld w:,L:uo, s - ~ re. than one and the ,al~ ofnonnaJ .:ol.11;.:, .~ p-~ is IG,,r-< than trse ocscr.ed c.olhgarivc proper!) of this solution fm)u. f'.JC! z:: d 1 , exhib;1 onJ:, .3 ox.id.cruon Stale io lanthanoid series 1 ' " ~ "" -"' ::- 0.-,.k L .,s,ed a; b"" '7:, a-a !Odofonn IS used as ~ tt'fi,-1::-_- tB Se.::=: zx -..-:;.-.e ~ correc: al"!.effi21h.e from tne c!Joices gn eo belo'A : fi1'v. ,=-:;; d ~ 1~ v.1ll f , e c.o:o-.:rless aq~..:s sr,n..'tion'' a"\:,:1 -:, Fe=-- Y,cu <c,c.i- u,-;--~ ::-..:~ tm1e: oi :>Oiling j)Oi.ms ofafk:. J i':alides IS. " Ji _. ::i1RB: _,. RCI ,,. RJ,.. Rf d;RO,.. Rf _,. RJ ,.. RBr PC. ,,. P..3 ,,. PJ _,c?J ,,. :IB ,.. PC ,,. RF oJf:eez. - g po::nt oi soh e:-n ~~ poi.::: of solution ....,.--_~ ;q.;:;: o; v .1h ~ II' : .: ...~ ~e:; ~ ~ ~.,~ :.o C1!:l ~ .i.i- :;-c et"" ;Lcoxc and f ~? d,Benedic:"~ scl~Lon J<. Jp--h~ dror:, 82Cr<r.r.u:na: _. _-...e;. =-=-.. ~t'-!- r :1 :il'..I:io~ Rt:a,.>:a : (Jr ..:._ .::,.~ ~ - - ...... DC _ : ir;. - ~ j)!:"' _: : \: ---t:. ~-e:~c~ . / ~ .. - ...~ " ~ _; : ; ~ - - ~ ~ ,: : ---= !:...- _;? -2..,;,,..,. .. ---~:e . ._ ~~ e~---a:1"~1. ,... o!" A'!l\1:.- u 1. t, i1 ~~ = ~;ct=.:...: ...r...~_.:-;, ~ ~ c.:' a_ ~.;:.::: 111 Page 3 of 7 1J ) lltllh A,,crtion and lh:n, 1111 111c lnl~l'. (' ii)A,,c r1ion: I Cl1Hll) but) I nlcohol upnn lwa1111c "1th conl 111\C >, ,11 I 11"rmunl~ l!" l'' ~mcth} I pmJl l -cnl lteus:on: I he fonnatlon ol' 2-mcth yl prOJl l-cnc 101,.c!> pince b} ~N1 mcchnni :,,n. (a) Hoth As,cn1on nm! Rco,on arc true und Rcn,un i, thl' rnrrcc.t cxJllnnntion nf ;\\:,crti on th) Both As~cr11on m1J Rco-.on urc true but llcu,on i, 11111 the correct cxplunution of J\\,ert, on (c) A!>Wl'li on is tnic hut Rclt'~on is fol sc. ~oth As~cr11on uml Reuson ore false. (C)C-nns1dcr the fullo,,i ng clcctrochcmicul cell ond an,,,cr the <111estion:. ll.kOV: 1 "1111111~' 131 IJ.76\1 n 1 M Af.NOJ Solu1iun (i)\Vritc a hulam:cd net ionit: cq11:.11ion for the ,,)()ntancous reactio n that takes place in the ,ell (ii)( ulculate the st:iml:11 u i:cl I potentiul I " fo1 the eel I reaction . Cili)l lu,, \\Ill the cell pnte111l:i l he afli:c.:tcd II Kl i, added tu Ag ' half-cell? / SEflT teN - I (21 M AftKS) fa,.. ,ion-l (i}Un rnilling liquid ' X' nnd Y' . Hllume ol rc-~ultin g ~olu11un dcc rca,cs \\ hot of u.:, 1Jt11.m horn Rauult', l:m i'.> , ho\\n h, the rc,ulting ~olutil>n" What ch1111g.: in 1cmpcraturl!type \\Ould ,1111 oh,cl\ t' .il1er 1111\1111,! liljllith ;,.. .inJ Y''.' I11 (ii)\\ h,11 li.1ppen ,,lwn ,,cpl.ic e the hl1,u<l cclh in ,, :11cr' Gi,e rc:1~011 Page- 4 of 7 Jfuc~tion-.3 Pl A 1'.~0 H.~ "-- B D1I HCJ C 200 .nm t ._ _ - ~- "-:.:. .o.: tTc:;o'l:.:.0:.:0:.:n.:..,.__ _ _ __,., D ( M aj or) Qucstion-4 Complete and balance the follO\\ ing chemica l cqumions: (ii)KiCr2O, ;,. H2SO4~ l hS 121 fluestion-5 Identify the compounds(A ). ( B).{C)and ( D) in the folio\, ing reaction: 121 (t,I l~COOH {SOCh) ( A) (N I I,) (I ) (Br./KOH + heat) (C) (NaNO~-rl K I.0 -5' C) ( D) Qucstion-6 Conduc1h it) or '.!x I o 3M mcthanoic acid is 8 :-. I o-~ Sc111 1 Calculat e it~ molar conductivil} and degree of dissocim ion If ),0m meth:moic acid i!> 404 S cm~ mo1 1 121 _,.Qucsrion-7 Ammgc the fo llowing as per the given in,1ructi on: 121 (i)C'H;OH. H~O. Cl>I 1(01-1. C:HsOH (decreasing order of acid strength) (ii)phcn ol. p-cresol. p-nirro phenol (inrrcas ing or<ler of acid strength) ..,(:)u~ tion-8 Gi, e onl" chemica l test to distinguish bet\\ een the follO\\ ing pairs of compounds 12 I (i)[than ol ond dimethyl ethl r I (ii)Anilinc and dimethyl uniline ,.f fieq ion-9(i) An aromatic compound A' on henting with ammonia and Cu~O at high pressure ~gl\es a . l hc compound 'B' on treatment with ice cold solution or NaNOz and HCI gi, es c ,,h1lh on heating "ith Cu/l ICI gives compound A' again. ldentif~ the compound A . s :md c \\'ri1e the name of the reaction for the comersion of B' 10 c. 121 l rt J ii)\\ rile !lalanccd chcm ,cal equutions fur the folio,\ mg: 1u 1-\1 lir.c \\Ith bromllll' ",lier l~I tl>l 4-niline "ith aenzo~ I chlMiut" uc,t ion- I t \\ file .1ppropri:Hc rc:m,n, foar the fo1l l,m ing. fo\hr -/ chl rme i, an clectn111 ,, ithdra\, ing group but. 1t j,, onho and p:ira J1rectm~ 111 l k t m>phil 1~ ,u. sti1U1i n in an:m:~ ' I~I Page 5 of 7 (ii)Sc" 3 is colourless in aqueous solution "here~ Ti- 3 is coloured. Qu~tioo-1 IAn aqueous solution containing 12.48g of Barium chloride in I 000g of water boils at I 00.10832''C. Calculate Lhe degree of dissociation of Barium ch loride. (K~ for \\oater = 0.52K kg mo 1 1 , at. wt. of Ba = I J7. Cl = J5.S) 121 SECTION - C (2 1 MARKS) Q uestion- l2The specific conductance of0.01 M solution ofacet1c acid at 298K is 1.65 x 10.j ohm 1 cm 1 The molar conductance at infinite dilution for 1-r ion ond CH,C00 1 are 349 I ohm 1 cm' mo1 1 and 40.9ohm 1 cm 2 mo1 1 respective!) . Calculate: 131 (i)MoUar conductance of the solution. (li)Degree of dissociation of CH1COOH. (iii)Dissociation constant for CH1COOH. ~ uesrion- 13 An organic compound ' A' on u-eatment with aqueous ammonia and heating fonn s compound ' B' which on heating with bromine and KOH form s a compound c of molecular fonnula CoH1N. Write the structures and IUPAC names of A', B, and c . Write the name of the reaction for the conversion uf s to 'C'. Write the balanced chemical reaction for Lhis name reaction. 131 fiuestion- 14 How will you obtain the following (Give balanced chemical equation): 131 (i)Benzoic acid from phenol (ii)Propan- l-ol 10 propan-2-ol (iij)Ethanol from Grignard' s reagent Q ucstion- 15 Explain lhc extraction of Potassium <.l ichromate from chromite ore. 181 (Wnte only balanced chemical reactions) Quest ion-16 (i)Aradhana visits a physician as she is suffering from rickets und joint pill in . Which fat soluble vi tam in shou Id the phy~idan presnibc to her? l 11 (ii)\omesh has put o few drops of vinegar in milk. What change do you think he obscr-ed rn the milk c1fier sometime? What is thi~ phenomenon f..n,own as':' Pl (iii)'...; ume the produu nf hydrolysis of sucrose. Is it a reduci ng sugar r non-reducing sugar'' 111 ' I ' ,. . I'HU" 6 ul 7 11 11 1 \,,1111 111111 , ., \ II l ' i\ l 1111111 1111 , .11h111111111111. 1 I 1 ,u1 ,111 11 ,11111111 p1 0:,~1m 11 1 fi K 11111 ' ' ~ I 111. 11h111 Ill\' d 1'!1", 11 I d 1~ ., 11 u,111111 ,ti II.I I 131 IH\l) \\1111 l,,1l1111,1,l ,hr1111,1,I , ,.11111111 , 11111l1r f11tl11\\IIII' 1111111~ rc,11.llflll IJI '-' 11 ,111111 (h ll 111 1h-l I 111 tt ~ 11l vl1111 1,11 (1 )W11111 rc11t1w11 tll( vm.1,11111, \ II ( , 11, I ;111,I I 111 lh, l11l l11\\l1111 t t:111. 1l1111 fJI bdbll A (.lur,111111- I 1'l01\ \ 11,!l-1 , ,,111p111111d ul M1111i:11110:,i.: (Al d1 ct1111po~c:. un hc1,1 i 11 ~ to lihcrntc oxygen 111111, 1 111p 11111HI, l I I l 1111d l t ' ) 11 I 11111111:11111:w 1ir, formed ( 'ornpuun d (( I rt:lll l\ with K ( JI I m the p 1, ,1 ml.' ,,1 1-.1\( h 11, 1 1 H ( Il l 0 11 lwnt,111! 111111p,1uml (( l 1\lth 1.nm.. ll, ',O nnd ',u( I liberate, 11 ~ , 111,h \ 1 1\, \\ i:;i, 11l1111f \\llh 11 ~1 111p111111,I (l)J 1111111111i:1111c~c fdcntil ) I\, ll. < uml I> und wrllc 1.a I Il l (.l u1 , 1i1111 1\ lll'I 1,11 \ h<1 ,, , ,11 h, I I ll\\'11 ' <JS!,,. !lll ll \I \ 11 lhlll\'t111 , ,11 11111111111( ,~ I (11-. lh:1, 11111111 111,,1.,1111 "' lh,: , 111\11 11111 s,, .... 1-r 11111 I " ' " I 'I ' ' < 111111 ,d 111 1 the 11 llt1ll \'C1l111tl, !-<1lu11, t'ic.:;1:, 111 172 4K \\ htlc pure l11ll1>1\tll)! . ll ' l.' 1-. l-1 111111 I ,1111I v,1p.i111 fll\' S\UIC 111 \\Ulc r Ill 131 OR (ih A tco-1!(1~ ~ " l e ~ ~Ag- ~ ec i.;.g - cc=- The standard reducrion porenliais of ~- ..\ a_-;d C.f- Cc e:e I. &0\ ' and ..r ..;, \ ~ -:r, el) .... k:, '\.'-~ a. t>= :i-~ :!'wf of th::> ecll ~ \\ 1. !Jie l~I i: ,~.., :::en~c:..~ of Cd:- is 0. 1~1 and Ag- is O ?'.1 ? =~n ... ;.-,. -.;:.c:::..me.(\.isl~ for uie .. o:-.,;!mon gn-en m 1c}abo,e"' .... j,11f" m:t: ate tZ\l. o: ;rmc1p!e w \,h1cb the following ohservacions confirm. ,, hen ~ 50couJoml' ::}: elta:-~~ :s ~ lh.-o:.igh a ~iurion of cow~= sulphate. 3. I - 5g of coppe:r is deposited on ::--.: ~-&. A:. 1.0: Co pper= 63.5 1 f11 ffiestiou-21 (i) .\a organic compound A ' wilhmolecu.lar fonnula C~;~ on reaction wrch r~un~ a--""ld g-1,es-a oompourn:l 'B". s on contr0lled oxidation gives compound ,,hich re6-ees 1Men s .ea.gen: :o ghe sih er mirror and compound o . B" reacts with n in th~ ~~ of ~on:. SJ!phurk acid 10 g ,H . a S\,eet smelling compound ldentif) A. B. C. D and E. Wria tte ~ jo, o: C whh ammonia.. (3.51 c (1.5) Ciijl~if:. .-\ B ard C::: the fotk \\ing reaction ak.K&H +C Heat

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