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ISC Class XII Sample / Model Paper 2025 : Chemistry

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Practice Paper (2024-25) General Instructions: This paper is divided into four sections - A, B, C and D. Answer all questions. Section A consists of one question having sub-parts of one mark each. Section Bconsists of ten questions of two marks each. Section Cconsists of seven questions of three marks each, and Section D consists of three questions of five marks cach. 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 [ ]. When solving numerical problems, all essential working must be shown. In working out problems, use the following data: Gas constant R= 1.987 cal deg mol-! = 8B14 JK' moll = 0.082 l dm atm K'mol! latm = 1 dm3 atm= 101.3 J. 1Faraday=96500 coulombs. Avogadro's number =6.023x 103 SECTION A - 14 MARKS Question 1 (A) Fill in the blanks by choosing the appropriate word(s) from those given in the brackcts: [log R, 1/T, deoxyribose, ribose, HCI, H,SO4, Anhydrous ZnClz, anhydrous AlCls, 1',2*, 3]) 1. The plot of versus has slopes equal to Ea/R. 2. In RNA, the sugar is but in DNA, it is 3. Lucas reagent is a mixture of conc. 4. Aldehyde gives and alcohol whereas ketones gives (B) Select and write the correct 1. alcohol on reduction. alternative from the choices given below: Identify correct order basic strength of methyl substituted amine in aqueous solution. a. (CH)2NH> CH3NH,>(CH);N b. (CH)3N> CH;NH2 > (CH)>NH [4x1] [Sx1] C (CH);N> (CH;);NH > CH;NH, d. CH;NH: > (CH)2NH > (CH;);N law is : 2. The mixture which shows positive deviation from Raoult's (a Acetone + Chloroform b. Chloroethane + Bromoethane c. Ethanol + Acetone d. Benzene + Toluene 3. Which of the following statements is corect? a. Boiling point of 1-chloropropane is lower than that of 2-chloropropane. b. SN reaction of I-chlorobutane is easier than that of 2-chlorobutane.t-sasfmeat c. SN reaction of cloroethane is difficult than that of chlorobenzene. Dipole moment of CH3CI is less than that of CH3I 4. Which is not correct for Amino Acid? a. It is component of protein structure. b. It has high boiling point c. Natural Amino Acid having D-configuration. d. Having characteristic of point. 5. Pick out the correct statement w.r.t. [Mn(CN)6] a. It is spd hybridised and octahedral b. It is dsp bybridised and square planar. C It is d'sp' hybridised and octahedral d. It is sp'd' hybridised and tetrahedral. (C) Read the following passage and answer the following questions: [3x1] Electrolysis is a process by which electric passes through a substance to produce a During electrolysis, the reactions occurringcurrent chemical change. at the clectrodes are the oxidation and reduction reactions. Therefore, the products of electrolysis can be predicted on the basis of electrode reactions. potentials of different The products of electrolysis depend on the nature of being used. If the electrode is inert such as gold or material being electrolyscd and the types of electrodes platinum, it does not take part in the chemical reaction and acts only as a source or sink for electrons. On the other hand, if the electrode is reactive, it takes the electrode reaction. Thus, the products of part in electrolysis may be different for inert and reactive electrodes. The products of electrolysis mainly depend upon different oxidising and reducing species present in the electrolytic cell and their standard electrode potentials. It may be noted that some electrochemical processes, though feasible, are so slow kinetically that at lower voltages, these do not seem to occur. a. Why sugar cannot conduct electricity in aqueous solution? b. At which electrode do oxidation and reduction takes place in electrolysis? c. Asolution of Ni(NO)2, is clectrolysed betwcen platinum clectrodes using acurent of 5.0 Afor 20 deposited at the cathode? min. What mass nickel will be =58.7 g mol!, 1F=96500 Cmol ") (Given: Atomic masss of Ni [2 1] (D) reaction of monohaloarene takes place at o- and pElectrophilic substitution positions. Assertion: i) deactivates the aromatic ring. Reason: Halogen atom is the correct explanation of assertion. reason are correct. Reason Both assertion and reason are incorTect. b. Both assertion and incorrect. correct but reason is is Assertion ofassertion c. reason 1s not the correct explanation correct, but are reason assertion and A Roth ii. equationk= Ae-Ea/RT gives the: relation between rate constant and temperature. Assertion: The Arhenius calculation of energy of activation can with the help of this Reason: The graph of log k 1/T is linear and be possible ofIA1. correct and [RJ gives correct explanation are both [R] Reason and [A] Assertion a. but [R] does not give correct explanation of [A). b. Assertion [A] and Reason [R] both are correct wrong. c. Assertion [A] is correct but Reason [R] is correct. d. Assertion [A] is wrong but Reason [R] is SECTION B - 20 MARKS [2] Question 2 How much electricity in terms of Faraday is required to produce : 1. 20.0 g of Ca from molten CaCl? (Ca=40gm/mol) 40.0 g of Al from molten Al:0;? (A-27gm/mol) [2 Question 3 Write the reactions to prepared phenol from Aniline and Cumene. Question 4 [2] Explain dehydrohalogenation (b-elimination) of alkyl halides. Qdestion 5 The rate of the chemical reaction doubles for an increase of 10 K in absolute Ea. (R= 8.314 J K-1 mol-l) temperature [21 from 298 K. Calculate Qhestion 6 VGive the structures of A and B in the following reactions. 6) CH,CH,Br A0DIALAH (H) CgHgNO, Re/HO (CHD0 [2) Question 7 [NiCN):] is square planar while [NiCl] 2 is tetrahcdral. Explain. Question 8 Explain Lucas test. Question 9 rcagcnts givcn in Column-JL. Xfateh the reactions given in Column-Iwith the suitable (2] Cohumn-Il (Reagents) Column-i (Reactions) (1) LiAH, WBerzopbenone - Diphenytmethane 2 DIBAL-H Bezdebyde - 1-Pherylethanol La (3) ZaHg)/Conc. HCI Q Qcobeunone - ydcheanal D Pbei beoee 4 CH,Mg8r Betaldetyde Question 10 reaction: 1.1 V. Calculate the standard Gibbs energy for the The standard electrode potential for Daniell cell is (2) Zh +Cu? () Zne) + Cus) Question 11 increasing boiling points: Arrange the following sets of compounds in order of their i. (21 Pentan-1-ol, butan-1-ol, butan-2-o1, ethanol, propan-1-ol, methanol. Pentan-1-oi, n-butane, pentanal, ethoxyethane OR (21 Question 11 Write the structure of product of the following reaction: (GH,CHJ),Ca + 2CH;COa SECTION C- 21 MARKS (3 Question 12 reactions: Giye the structures of A, B and C in the following LIAH B HNO c CH,CHHBr ii. GH,NO, Fe/HCl A HNO GHOH, c [3 Question 13 B (molar mass I80 g mol'). The liquid of g 1000 in dissolved was mol-) 100 gofliquid A (molar mass 140 g vapour pressure of pure liquid Aand its the Calculate tor. 500 to be found +apour pressure of pure liquid B was pressure of the solution is 475 Torr. vapour total the if solution the vapour pressure in Question14 [31 Question 15 [3] acid to give a An organic compound (A) (molecular formula C 8 HI6 0 2 ) was hydrolysed with dilute sulphuric earboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration of compound(A). gives but-1-ene. Write equations for the reaction involved. State IUPAC name Giye reason Transition elements exhibit higher enthalpies of atomisation. than Fe*. In aqueous solution, C* is stronger reducing agent The second ionisation enthalpy of Cu is higher than Zn. ii. [3) Question 16 Calculate its degree of dissociation wThe molar conductivity of 0.025 molL- methanoic acid is 46.1 Scm'mol. (HCOO ) = 54.6 Scm'mol, and dissociation constant. Given A"H*=349.6 Scm'mole and 2 Or [3] Question 16 at 1 bar pressure and 300 K tcmperature In electrolysis of CuClz, 2.0 ampere current is passed through solution cathode? [Cu = 63.5, Cl=35.5] for 1 hour, so calculate how much product is obtained at anode and (3] Question 17 What happens when D-glucose is treated with the following rcagents: i. HI Br/H0 iii. HNO, [3] Question 18 The following results have been obtained during the kinetic studies of the reaction: 2A +B C+D Esperiment AJ/ BI/ mol L-l mal L-1 Initial rate of Tormation of |D/mol L-l min-l 03 0. 6.0 x 103 02 7.2 x 102 2.88 x 10-! 0.1 2.40x 1o-2 0.3 IV 04 Determine the rate law and the rate constant for the reaction. SECTION D - 15 MARKS Question 19 Write the chemical equations to illustrate the following name reactions. (a) Wolff-Kishner reduction (b) Aldol condensation i (c) Cannizzaro reaction Account for the following. [5 CH3COCH3 reactive with HCN than more is CHO (a) CH3 than phenol. (b) Carboxylic acids are Question 20 stronger acids Write the IUPAC names [Co(NH3)4 SO4] NO, of the following. (a) ii (b) K[Pr(NH)Cl3] compounds? by the following pairs of exhibited is isomerism of type What [PtBrz (NH3)4]Cl; (a) (PrClz (NH3)4] Brz and [Cr(NCS) (H; 0)s]* and (b) [Cr(SCN) (H, O)s]*ionised it form precipitate, when AgNO, sol.s: Will water? in dissolved when How does Ka[PtCl4] get your answer. is added to it? Give a reason for [5) components liquid K, the vapour pressures of the two Heptane and octane form an ideal solution. At 373 vapour pressure of a mixture of 26.0 g of be the What will respectively. 46.8 kPa are 105.2 kPa and heptane and 35 g of octane ? dissolved in 20 g of Question 21 formula AB2 and AB4. When Two elements A and B form compounds having K. point by 2.3 K whercas 1.0 g of AB4 lowers it by B.1.3 benzene (CsH6), lg of AB2 lowers the freezing mol. Calculate atomic masses of Aand molar depression constant for benzene is 5.1 K kg The Or Question 21 (5] equal 2g of benzoic acid (C&HsCOOH) dissolved in 25 g of benzene shows a depression in freezing point to 1.62K Molal depression constant for benzene is 4.9K kg mol-. What is the percentage association of acid if it forms dimer in solution? 1.00 gof anon-electrolyte solute dissolved in 50 gof benzene lowered the freezing point of benzene by 0.40 K. The freezing point depression constant of benzene is S. 12 Kkg molr. Find the molar mass of the solute.

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