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ISC Class XII Prelims 2026 : Chemistry (Smt. Sulochanadevi Singhania School, Thane)

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Savitri Prajapati
Smt. Sulochanadevi Singhania School, Thane

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SMT. SULOCHANADEVI SINGHANIA SCHOOL, THANE. Class Subject 12 Exam Date Chemistry Preliminary exam Mark s 08/01/2026 70 Time Total No. of Printed sides 3 hrs 6 Instructions to Candidates You are allowed an additional fifteen minutes for only reading the question paper. You must NOT start writing during the reading time. This question paper has 6 printed pages. It is divided into four sections and has twenty one questions in all. Answer all questions. Section A has fourteen subparts. Each question carries 1 mark. While attempting Multiple Choice Questions in Section A, you are required to write only ONE option as the answer. 8. Section B has ten questions. Each question carries 2 marks. 9. Section C has seven questions. Each question carries 3 marks. 10. Section D has three questions. Each question carries 5 marks. 11. Internal choices have been provided in one question each in Sections B, C and D. 12. The intended marks for questions are given in brackets [ ]. 13. All working, including rough work, should be done on the same sheet as, and adjacent to the rest of the answer. 14. Balanced equations must be given wherever possible and diagrams where they are helpful. 15. When solving numerical problems, all essential workings must be shown. 16. In working out problems, use the following data: Gas constant R=1 987cal deg-1mol-1 = 8 314JK-1mol-1 = 0 0821dm3atmK-1mol-1, 1 l atm =1dm3atm = 101 3 J. 1 Faraday=96500 coulombs. Avogadro s number = 6 023 1023. Section A-14 Mark Question 1 A) Fill in the blanks by choosing the appropriate word(s) from those given in the brackets: [4 x 1] 3 2 [sp d , greater, high, outer, lesser, iodoform, inner, sodium iodide, free iodine, low, osmosis, reverse osmosis, positive, negative] (i) Liquid A and B on mixing show rise in temperature, this shows that A-B force of interaction is _________ than A-A and A-B force of interaction and solution of A-B shows ________ deviation from Raoult s law. (ii) Outer orbital complex involves _________ hybridization and are _________ spin complexes. (iii) Acetone on treatment with iodine and sodium hydroxide gives _________ which is used as an antiseptic due to liberation of _______ (iv) Water retention due to high salt intake occurs due to _________ and _________ is the phenomenon occurs during dialysis of such patients suffering from kidney disease. S M T. S U LO C H A N A D E V IS IN H A N IA S C H O O L, TH A N E 1. 2. 3. 4. 5. 6. 7. B) Select and write the correct alternative from the choices given below. (i) Which of the following is not expected to show optical isomerism: (a) [Co(en)(NH3)2Cl2] (b) [Co(en)3] 3+ (c) [Co(en)2Cl2]+ (d) [Co(NH3)3Cl3] 1 [7 1] Consider the reaction G +bH products. When concentration of both G and H is doubled the rate increases 8 times. However when concentration of G is doubled keeping the concentration of H constant, the rate is doubled. The order w.r.t H of the reaction is (a) 0 (b) 1 (c) 2 (d) 3 (iii) Insulin is a (a) sugar (b) vitamin (c) lipid (d) protein (iv) Propan-1-ol and propan-2-ol can be distinguished by: (a) oxidation with KMnO4 followed by reaction with Fehling solution (b) oxidation with acidic dichromate followed by reaction with Fehling solution (c) oxidation by heating with copper followed by reaction with Fehling solution (d) oxidation with concentrated sulphuric acid followed by reaction with Fehling solution (v) To prepare C6H5OC2H5, reactants taken are: (a) C6H5I and C2H5OH (b) C6H5OH and C2H5I (c) C6H5OH and C2H5OH (d) C6H5I and C2H6 (vi) Given below are two statements marked Assertion and Reason. Read the two statements carefully and select the correct option. Assertion: Secondary aliphatic amines react with nitrous acid to form aliphatic diazonium salts which being unstable, liberate nitrogen gas quantitatively. Reason: Nitrogen gas evolved on reaction with nitrous acid can be used for the estimation of proteins and amino acids. (a) Both Assertion and Reason are true and Reason is the correct explanation for 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. (d) Both Assertion and Reason are false. (vii) Given below are two statements marked Assertion and Reason. Read the two statements carefully and select the correct option. Assertion: Carbonyl compounds take part in nucleophillic addition reactions. Reason: These reactions are initiated by nucleophillic attack at the electron deficient carbon atom. (a) Both Assertion and Reason are true and Reason is the correct explanation for 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. (d) Both Assertion and Reason are false C) Read the passage carefully and answer the questions that follow. [3 1] Standard electrode potentials of a large number of electrodes have been measured using standard hydrogen electrode as the reference electrode. The arrangement of elements in order of increasing electrode potential values is called electrochemical series. This series is also called as activity series. With the help of this series, we can predict the relative oxidizing or reducing strengths of substances. We can also construct an electrochemical cell and predict the feasibility of the reaction. The standard electrode potentials (E ) of metals are given as: (a) Mg2+/Mg = -2.37 V (b) Cu2+/Cu = +0.34 V (c) Fe2+/Fe = -0.44 V (d) Zn2+/Zn = -0.76 V (e) Ag+/Ag = +0.80 V (i) Arrange the metals in the increasing order of their reducing power. (ii) From the given metals which metal will be the best choice to prevent corrosion in iron? (iii) Calculate the emf of the cell containing iron and zinc electrodes. S M T. S U LO C H A N A D E V IS IN H A N IA S C H O O L, TH A N E (ii) 2 SECTION B 20 MARKS Question 2 [2] i) FCI mandates that the conc. of microbial decay is unacceptable with max 30% change from the initial concentration If the manufacturing date of a canned food is 1st June 2021, what should be the expiry date of this food as per the mandate of FCI? (Given the average rate constant of microbial decay is 0.001 units day , assume microbial decay follows first order kinetics) S C H O O L, TH A N E Question 3 [2] What will be the vapour pressure of a 1 molal aqueous solution of MgCl2, assuming dissociation of MgCl2 to be 70 percent? (Vapor pressure of pure water at 25 C is 23.8 mmHg) S U LO C H A N A D E V IS IN H A N IA Question 4 [2] Shown below is a step-wise process for the formation of an orange-coloured crystalline compound C. Identify the compound C and write the chemical reactions to show the formation of compounds A, B, and C. Question 5 (a) Name the reagents used in the following reactions: (i) Oxidation of primary alcohol to carboxylic acid. (ii) Oxidation of primary alcohol to aldehyde. (iii) Bromination of phenol to 2,4,6-tribromophenol. (iv) Conversion of propan-2-ol to propene. [2] S M T. Question 6 [2] (a) Arrange the following as per the instructions given: (i) 1-bromo-3-methylbutane, 2-bromo-2-methylbutane, 2-bromo-3-methylbutane (increasing order of reactivity to SN2 mechanism). (ii) C2H5NH2, C6H5NHCH3, (C2H5)2NH, C6H5NH2 (decreasing order of pKb values). Question 7 [2] (a) What type of cell is mercury cell ? Why is it more advantageous than Leclanche cell ? (b) The conductivity of 0 20 M solution of KCl is 2 48 10 2 S cm 1. Calculate its molar 0 conductivity and degree of dissociation ( ). [Given : 0 + = 73 5 S cm2 mol 1 = 76 5 S cm2 mol 1] Question 8 [2] The rate of a reaction at 700K is 4 times faster than the rate at a lower temperature T. The energy of activation is 20.19 103 J/mol and the rate constant at 700K is 0.08s-1 . (i) Calculate the rate constant at temperature T. (ii) Find temperature T. (use R = 8.314 J/mol K) Question 9 (i) Give a simple chemical test to distinguish between (a) Phenol and Benzoic acid 3 [2] (b) Butanal and Butanone Or (ii) An organic compound (A) ( molecular formula C6H16O2)was hydrolysed with dilute sulphuric acid to give carboxylic acid (B) and alcohol(C). Oxidation of (C) with chromic acid produces (B). (C) 0ndehydration gives but-1-ene. Write equations for the reactions involved. Question 10 [2] Complete and balance the equation: (i) K2Cr2O7 + H2SO4 + H2S ______ +______+_______+______ (ii) KMnO4 + H2SO4 + FeSO4 ______ +______+_______+______ S U LO C H A N A D E V IS IN H A N IA S C H O O L, TH A N E Question 11 [2] How will you convert (give balanced chemical equation): (i) Ethanoic acid to methanamine (ii) Cholorobenzene to p-chloroaniline Section C - 21 Marks Question 12 [3] Alcohols are the compounds that have one or more hydroxyl groups bonded to aliphatic carbon atoms while phenols are the compounds which have one or more OH groups bonded to aromatic ring. Ethers have R-O_R as the functional group. They may be aliphatic as well as aromatic. (i) Write chemical reaction for the conversion of phenol to salicylic acid. (ii) Old stock of ether should be handled very carefully, why? (iii) Convert formaldehyde to ethanol. Question 13 [3] Explain: (i) Transition elements show high melting point. (ii) Zirconium(Zr) and Hafnium(Hf) are difficult to separate. (iii) Salts of cupric(Cu2+) ions are coloured while salt of cuprous(Cu+1) ions are colourless. [3] S M T. Question 14 Complete the following reactions: (i) C6H5N2Cl + H3PO2 + H2O (ii) CH3CH2CH2Br + AgCN (iii) CH3CH=CH(CH3)2 + HBr Question 15 [3] Answer the following questions: (i) Identify and give any one point of difference between the protein present in the hair and protein present in egg albumin. (ii) Both glucose and sucrose have aldehydic group, then why does only glucose reduces Fehling s reagent and not sucrose? (iii) Doctor advised a 50 year old woman enough exposure to sunlight and addition of fish and egg yolk to her diet. What is the possible disease diagnosed by the doctor? Question 16 [3] (i) Answer the following: (a) A current of 1.5 ampere was passed through an electrolytic cell containing AgNO3 solution with inert electrodes. The weight of silver deposited was 1.5 g. Calculate the 4 time period for the flow of current.( Molar mass of Ag = 108 g/mol, 1F = 96500 Cmol-1) (b) The cell in which the following reaction takes place 2Fe3+(aq) + 2I- 0 2Fe2+(aq) + I2(s)has = 0.236 V at 298 K. Calculate a G and equilibrium constant of the cell reaction. Or (ii) (a) Write the cell reaction and calculate the emf of the following cell at 298 K: Sn(s) Sn2+(0.004M) H+(0.02M) H2(g)(1Bar) Pt(s) 0 [ : 0 2+ = 0.14 V, / = 0.00V] + / 2( ), (b) State Faraday s second law of electrolysis. [3] S C H O O L, TH A N E Question 17 28000 (a) The decomposition of hydrocarbon follows the equation k = (4.5 x 1011 sec-1) , Calculate the activation energy (b) Why is molecularity applicable only for elementary reactions and order is applicable for elementary as well as complex reactions ? (c) For the reaction A+ B products, the rate of reaction at different concentration of A and B are given below [B] 3M 3M 2M S U LO C H A N A D E V IS IN H A N IA Exp.no [A] 1 0.1M 2 0.2M 3 0.2M What is the order with respect of A and B? Rate(moll-1sec-1) 3.1 x 10-3 12.4 x 10-3 12.4 x 10-3 S M T. Question 18 [3] (a) Give plausible explanation: Why do primary amines have higher boiling point than tertiary amines? (b) Give structures of A and B in the following: CH3CONH2 NaOH + Br2 A NaNO2+ HCl B (c) Arnika entered the lab and found that there were three test tubes labeled as A, B and C containing some liquid. She was told that one contains aromatic amine other two are primary and secondary amine. Help her to distinguish them with a good chemical test. Section D (15 Marks) Question 19 [5] (a) Write balanced chemical equation to carry out the following conversion in not more than 2 steps: (i) Propanone to 2-chloropropane (ii) Ethanol to 3-hydroxy butanal (iii) Acetic acid to acetone (b) Write reactions involved in the following: (i) Hell-Volhard-Zelinsky reaction (ii) Benzoin condensation Question 20 (a) Answer the following (i) State Raoult s law for a solution containing volatile components. (ii) How Raoult s law is a special case of Henry s law ? 5 [5] (iii) Why can azeotropic mixture not be separated by fractional distillation ? (b) The freezing point of a solution containing 5 g of benzoic acid (Molar mass=122 g mol 1) in 35 g of benzene is depressed by 2.94 K. Calculate the percentage association of benzoic acid if it forms a dimer in solution. Cryoscopic constant for benzene is 4.9 K Kgmol-1 Or Answer the following: (a) In an experiment Test Tube 'A' contains FeSO4(NH4)2SO4.6H2O solution and test tube 'B' contains K3[Fe(C2O4)3] solution. On adding few drops of KSCN in the two test tubes, solution of one of the test tubes turns into red. i) Identify which out of two solutions in the test tubes 'A' or 'B' turns into red? ii) Give reason why does one solution give red colour precipitate with KSCN but other solution does not show any change. (b) Write the IUPAC name of i) [Cu(NH3)4][PtCl4] ii) [Co(NH3)3Br(NO2)]2+ (c) What is chelate effect? Amongst [Ag(CN)2]-1 and [Co(en)3]3+ which complex ion is more stable? S U LO C H A N A D E V IS IN H A N IA (ii) S C H O O L, TH A N E Question 21 [5] (i) Answer the following: (a) Write the formula of the following coordination complex: (i) diaquasilver(I) dichloridoargentate(I) (ii) Diamminetetraqauairon(II) sulphate (b) A co-ordination compound [Co(x)6]3- shows d2sp3 hybridisation. (i) Identify the nature of ligand x as weak or strong. (ii) Explain how does the presence of ligand x affect crystal field splitting energy 0 and pairing energy P. (atomic number of Cobalt is 27) (c) Write the formula of ionization isomer of [PtCl2(NH3)4]Br2 and its IUPAC name S M T. ******************************** 6

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