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PRE-BOARD exAM IN~llO N 2024- 25 SUBJECT - CHEMISTRY STANDARD - XII Time:3HRS. ------------------------- M.M.:7 0 ---------- -------------------------------------- (Candidates are allowed additional 1 5 minutes for only reading the paper. They must NOT start writing during this time.) ------------------------ ---------------------------------------- This paper is divided into four sections - A, B, C and D. Answer all questions. . J Section - A consists of one question having sub-parts of one mark each. Section - B consists of ten questions of two marks each. Section - C consists of seven questions of three marks each, and .._ Section - D consists of three questions of five marks each. Internal choices have been provided in one question each in Section B, Section C and Section D. All working, including rough work, should be done on the same sheet as, and adjacent to the rest of the answer. The intended marks for questions or parts of questions are given in brackets l). Balanced equations must be given wherever possible and diagrams where they are helpful. When solving numerical problems, all essential working must be shown. In working out problems, use the following data: 1 Gas consta nt R = 1.987 cal deg_, mor = 8.314 JK1 mor1 = 0.0821 dm3 atm K 1 mor' 1 L atm = 1 dm3 atm = 101.3 J, 1 Faraday= 96500 coulombs, Avogadro's number = 6.023 X 1023 -------------------------------------------------------------------------------------------- XII-CHEMISTRY 1 l! l!lji4i;l; l l~ ~- -- - -- -- -- 11U '.p.Di rnl!IIIF SECTION A _ l 4 MARKS Question 1 A) Fill in the blanks by choosing th e appro priate word(s) from those given in the brackets: [does, increases, does not ko , , 5, ethano1, {R]O , 4, K~, ethene , cN , remains same, decreases, k[R} 0} i) ii) For a zero order reaction, rate d,aeg nA/, dep end on the concentration of any reactant. Therefore, it can be written as rate= k.. 0 Th e quan.tity of ions generated upon the dissolution of potassium ferrocy,:nide, K3[Fe(CN)J, in water is Lt . This indicates that functions as the ligand in the coordination com pound. Chloroethane reacts with aq. KOH to form ekltDMot main product while alcoholic KOH form e,tt;~,i>J , as the chief product. IJW As the carbon chain length of alcohols incr eases, the boiling point ~ and the solubility in water ~ CN iii) iv) B) Select and write the correct alternative from the choices given below: i) How long would it take to deposit 50 g of Al from an electrolytic cell containing Al 2Q 3 using a current of 105 amperes? a) 1.5 4h c) 1.3 2h ii) ~ d) l.4 2h 2.1 5h Of the following complex ions, which is diama gnetic in nature? c) (CuCl 4 ] 2- d) [CoF6]3- iii) Transition elements form alloys easily bec ause they have . . num ber a) Same atomic b) Same electronic conf1gurat1on size d) None of the above JjJ ' Nearly same atomic - doe iv) Which of the followmg s not rea ct with Hinsberg reagent? b) (CH3)2NH a) C2H5NH2 d) CH 3CH(NHJCH 3 \_%(CH 3)3N XII-CHEMISTRY 2 t Sf!fP-5 v) . . The solution that forms maxi mumb 01 hng azeotropes is a) Carbon disulphide - Acetone b) Benzene -Toluene A Acetone - Chloroform . d) n-Hexane - n-Heptane vi) Assertion: H. ion cannot oxidize copper. 2 Reason: Reduction potential of Cu /cu is greater than H /H. \)Y Both Assertion and Reason are true and Reason is the correct explanation of Assertion. b) Both Assertion and Reason are true but Reason is not the correct explanation for Assertion. c) Assertion is true but Reason is false. KAssertion is false but Reason is true. vii) Asserti~n: Aliphatic amines are weaker base than ammonia. Reason: +I effect of alkyl group results in high electron density on nitrogen atom. a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion . ' ' b) Both Assertion and Reason _~r~ true but Reason is not the correct explanation for Assertion. c) Assertion is true but Reason is false. JiY Assertion is false but Reason is true. c) Read the passage given below carefully and answer the questions that follow. In order to account for the extent of association and dissociation. Van't Hoff introduces a factor called van't Hoff factor (I). It is defined as: the ratio of the normal (theoretical) and expected (observed) Molar mass. In case of association, the magnitude of experimental mass is greater than theoretical molar Mass. In case of dissociation, the magnitude of experimental mass is less than theoretical molar Mass. In case of no association or dissociation, the magnitude of experimental molar mass is equal to theoretical molar mass, so varD Hoff faf or . 1-ex. To/; / t - 1;..~ p - /-0('_; f)..A -78 value 1s equal to one. _ ot,>,, ~ i - r;. . 1 i) What is the van't Hoff factor fQr a compouna w_hj ~ undergpt~ in ll . . . . ?~ = ND.~ ~ ~ a_MC<!I(~ o,, 6_4-dimensation in an organic solvent . Iv ~ u,,.U,aLW 1iiJ:.&i = ~ A compound X undergoes tetrame ~1zation fn given organic solvent. What is the van't Hoff factor? 4 X ~ X4 i, ~ 0 + _j_ -I ::::. u~ 1 XII-CHEMISTRY X'-"t J_ xu , t ~~ , -t~t / - I O a 4b k 1 / f _ - E:3-,( 'f 3 , iii) How muc h mol ecu lar 1nass . . . ,.. 1 of col I1gat1ve prop ertie s? l"'\.O (J A-i ~~ f;-f '-'t.tu>(e__,,) Cl Is obta ined experimentally usin 9 Na M { ~ 0...l)oo~ 9In\h' l l,,W, " " -::.: b ~ ..i :lcH . r ,. j, . - ;, :J I.J J, SECTION B _, 20 MARKS Que stio n2 i) Arrange the follo wing ;f1:;, < ~ L. . / cornP..ou nds in the,..$rm5reasm g orde r of thei r basi c stre ngth s: ~ ~ v1.i f:4.,e ~ A P {.et"1..(li~Aniline, p-nitro aniline, p-toluid ite p- ~ J,iw, r:'r lJ\i ' '1j.~ / 7o't ii) Phenol exh1b1ts a sign if ~ Question 3 ican tly shorter C O bond com pared to ethanol. Why? Give a reason for each of the f . . o11 owang , 1) Salt s of cup rous (Cu ) exh ibit col ions appe ar colorless, while salts of cupr ic (Cuh) ions or. ii) Zinc, with an atom b . IC nurn er of 30, not considered a tran sitio n element. Quest1o n4 Give balanced chemical equations to convert the follo wing: i) Ethanol to m ethy lam ine ii) Benz ene to Biph eny \ Que stio ns Answer the following: i) Why joes ~Cr 20 1act as a powerful oxidizing agent in acid ic medium? ii) Why doe s Mn( II) ion show maximum paramagnetic character amongst the biva lent ions of first tran sitio n series? Que stio n6 Show the following chemical reactions a) Clem men son 's Red uctio n b) Hun dsd ieck er Rea ction Que stio n7 Dry cells are commonly used in clocks, torches, calculators fam iliar type of commercial cells. etc. They are the most a) What acts as anode and cathode in dry cell? b) Which che mica l com pou nds are filled between anod e x n-OHEMlSTRY and cath ode of this cell? 4 Question 8 . I eactio What happens when (write chemic~ ~ ns only) Acetaldehyde with hydroxyl amine 8) tiie Presence of NaOH followed by acidification? b) Phenol reacts w,t h Co2 in ~ Question 9 .. h Rakesh mixes 0.30 g of acetic acid wit 1O0 9 of benzene and notices that the boiling point increases ~y o.o533 C. Calculate the molecular weight of acetic acid? Also, based on th ,s, what can we say about the form of the acetic acid molecules in the solution? (Given, Kbfor benzene is 2. 53 Kkg mor,, and the atomic weights are C= 12, H =1, 0 = 16) Question 10 i) Why does o-toluic acid exhibit higher acidic strength than benzoic acid? ii) How will you obtain ethanoic acid from ethyl cyanide ?(Write chemical reaction only.) Question 11 Explain why -'i) The melting and boiling points of Zn, Cd, Hg are low. ii) A transition metal exhibits higher oxidation states in oxides and fluorides. SECTION C - 21 MARKS Question 12 The following results have been obtained during the kinetic studies of the reaction: 2A+B~ C+D Experiment [A]/moll - 1 [B]/ mo IL - 1 Initial rate of formation of D/moll - 1min- 1 I 0. l 0.1 6.0xl 0-3 7.2xl 0-2 0.2 II 0.3 2.88xl 0-1 0.4 0.3 Ill 2.40xl 0-2 0.1 IV 0.4 Determine the a) Ratelaw XII-CHEMISTRY 5 b) Rate constant for the reaction c) Overall order of reaction Question 13 I) Arrange the following compounds in the ascending order of their basic strength and give reasons for your answer: Methylamine, Aniline, Ethylamine, Diethyl ether ii) Propanamine and N, N-dimethylrnethanamine contain the same number of carbon atoms, even though propanamine has higher boiling point than N, Ndimethylmethanamine. Give reason . Question 14 i) Name the bases present in RNA? Which one of these is not present in DNA ii) Write the chemical equation for the reaction of glucose with HI. iii) Water soluble vitamins must be supplied in diet regularly. Why? Question 15 i) What type of deviation from Raoult's Law is expected when phenol and aniline are mixed with each other? What change in the net volume of the mixture is expected? Graphically represent the deviation. ii) The vapour pressure of pure water at a certain temperature is 23.80 mm Hg. If 1 mole of a nonvolatile non-electrolytic solute is dissolved in 100 g water, Calculate the resultant vapour pressure of the solution. Question 16 Identify the compounds [A], [B] and [C]. ~ (i) ~ CH 3CI Anhyd. AICl3 KMnOiH+ (il) CH 3CHO A A Cl2 (1 mole) hv NH 3, Heat B B aq. KOH Br2/Na0H C C Question 17 i) How will the following be obtained? (Give chemical equations only) a) lsopropyl alcohol to iodoform b) 2-Chloropropane to 1-propanol c) Aniline to chlorobenzene XII-CHEMISTRY 6 90 18 s. If r explosion, one of the products is Sr with half-life of 28.1 year auestion es of a newly born baby instead of calcium. nuc1ea bon the in rbed abso aunn9 tI . . f 9osr wa 5 O it rs not lost metabolically. years 10 after in rema will h fit 1 g Howrnuc o SECTION D - 15 MARKS . : wmg follo the of each for . reason . . . . i) G,vea to Grignard's reagent for the rior supe d Dialkyl cadmium Is considere .d a) preparation of ketones from acr chlorides . position but not b) Benzoic acid undergoes nitration predominantly at meta Question 19 at ortho and para positions. its three ii) An organic compound with the molecular formula C1H1N0 2, exhib st melting point. isomeric forms. Among them, isomer 'A' possesses the highe molecular formula Upon reduction, 'A' transforms into compound 'B' with the C results in the C1H1N. Subsequent treatment of 'B' with..NaNO/HCI at 0-5 tion with H3 P0 2 , it formation of compound 'C'. Further, when 'C' undergoes a reac tion with Cr0 2 Cl 2 converts to 'D' with the formula C1H8 . 'D', upon additional reac ide the structural followed by hydrolysis, gives rise to 'E', identified as C1H60. Prov tions involved in representations of compounds A to E and the chemical equa converting Dto E. Question20 : i) Consider the complex, Na 2[Ni(CN)J, and answer the following a) State whether the complex is paramagnetic or diamagnetic. 2 b) What is the state of hybridization of Ni ion in the complex? iguration of d4 in ii) On the basis of Crystal Field Theory, write the electronic conf terms of t 29 and eg in an octahedral field when /l > P. excess AgN0 3, 2 iii) When a coordination compound CrCla.6H20 is treated with moles of Ag Cl are precipitated per mole of the compound. Write: a) The structural formula of the complex b) IUPACnameofthecomplex 0 XII-CHEMISTRY 7 Question 21 i) a) Ca lculat e the degree of dissociation of 0.0024 M CH3 COOH if conductivity of the solution is 8.0 x 1o ss cm '. [Given, >..: . = 349.6 \ /\c H C00 3 b) . = 40.9 s cm mor 2 s cm 2 mor 1 and, 1 ] Calculate the EC1!11 and ~G of the cell where t he following cell reaction ta kes place: Ni(s) + 2Ag (0.002 M) - Ni2 (0.160 M) + 2Ag(s) (Given : E~;2 ,N; =-0.25 V; E~9.,A9 =Q.80 V) OR ii) a) Find the cell constant and specific conductance for a cell by examining the resistance of a decinormal salt solution situated between two platinum electrodes. The electrodes, spaced 1.8 cm apart with a collective area of 5.4 cm2, exhibit a measured res istance-of ~Oohms. Calcul~te the cell constant and specific conductance of the solution using the given di mensions and resistance value. b) State two functions of salt bridge in electrochem ica I eel I. c) Calculate the potential of the following cell reaction at 298 K. Sn .. (1 .5 M) + Zn(s) ~ sn 2 (0.5o M) + Zn 2 (2.o M) 0 The standard potential E of the cell is 0.89 V. Whether the potential of the cell will increase or decrease, if the concentration of Sn 4 is increased in the cell? 000 0 0 XII-CHEMISTRY I JIE i M N'i .f W -J...___
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