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Class 12 CBSE 12th Board 2016 : Chemistry

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Lokam Sai
Columbia Convent School, Indore

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SET 1 . Series : ONS/1 Code No. . 56/1/1/D - - Roll No. Candidates must write the Code on the title page of the answer-book. - 11 - - - - 26 , - 15 - 10.15 10.15 10.30 - Please check that this question paper contains 11 printed pages. Code number given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. Please check that this question paper contains 26 questions. Please write down the Serial Number of the question before attempting it. 15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period. ( ) CHEMISTRY (Theory) : 3 : 70 Time allowed : 3 hours Maximum Marks : 70 : (i) (ii) - 1 5 - 1 - 6 10 - 2 - 11 22 - 3 - 23 4 - 24 26 - 5 , (iii) (iv) (v) (vi) (vii) 56/1/1/D 1 [P.T.O. General Instructions : (i) All questions are compulsory. (ii) Questions number 1 to 5 are very short-answer questions and carry 1 mark each. (iii) Questions number 6 to 10 are short-answer questions and carry 2 marks each. (iv) Questions number 11 to 22 are also short-answer questions and carry 3 marks each. (v) Questions number 23 is a value based question and carry 4 marks. (vi) Questions number 24 to 26 are long-answer questions and carry 5 marks each. (vii) Use log tables, if necessary. Use of calculators is not allowed. 1. CH3 CH CH2 Cl CH3 CH2 CH Cl SN1 | | CH3 CH3 ? Out of CH3 CH CH2 Cl and CH3 CH2 CH Cl, which is more reactive | | CH3 CH3 towards SN1 reaction and why ? 2. NaOH Cu2+ On adding NaOH to ammonium sulphate, a colourless gas with pungent odour is evolved which forms a blue coloured complex with Cu2+ ion. Identify the gas. 3. , ? What type of magnetism is shown by a substance if magnetic moments of domains are arranged in same direction ? 4. : NH2 Br Br Br Write the IUPAC name of the given compound : NH2 Br Br Br 56/1/1/D 2 5. Write the main reason for the stability of colloidal sols. 6. , , : (i) ? (ii) ? (iii) ? (iv) ? From the given cells : Lead storage cell, Mercury cell, Fuel cell and Dry cell Answer the following : (i) Which cell is used in hearing aids ? (ii) Which cell was used in Apollo Space Programme ? (iii) Which cell is used in automobiles and inverters ? (iv) Which cell does not have long life ? 7. FeCr2O4 NaOH , (A) (B) (B) KCl (C) (i) (A), (B) (C) (ii) (C) : (i) 8MnO 4 + 3S2O23 + H2O (ii) Cr2O27 + 3Sn2+ + 14H+ When chromite ore FeCr2O4 is fused with NaOH in presence of air, a yellow coloured compound (A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl forms a orange coloured crystalline compound (C). (i) Write the formulae of the compounds (A), (B) and (C). (ii) Write one use of compound (C). OR Complete the following chemical equations : (i) 8MnO 4 + 3S2O23 + H2O (ii) Cr2O27 + 3Sn2+ + 14H+ 56/1/1/D 3 [P.T.O. 8. CrCl3.6H2O AgNO3 , AgCl (i) (ii) When a co-ordination compound CrCl3.6H2O is mixed with AgNO3, 2 moles of AgCl are precipitated per mole of the compound. Write 9. (i) Structural formula of the complex. (ii) IUPAC name of the complex. : 2NH3(g) (i) (ii) Pt N2(g) + 3H2(g) = k k Pt For a reaction : 2NH3(g) N2(g) + 3H2(g) Rate = k 10. (i) Write the order and molecularity of this reaction. (ii) Write the unit of k. : H2SO4 2 CH3CH2OH CH3CH2 O CH2 CH3 413 K Write the mechanism of the following reaction : Conc. H2SO4 2CH3CH2OH CH3CH2 O CH2 CH3 413 K 11. : (i) C Cl CH3 Cl C Cl (ii) (iii) SN1 Give reasons : (i) C Cl bond length in chlorobenzene is shorter than C Cl bond length in CH3 Cl. (ii) The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride. (iii) SN1 reactions are accompanied by racemization in optically active alkyl halides. 56/1/1/D 4 12. 250 pm f.c.c. 300 g 2 1024 , An element crystallizes in a f.c.c. lattice with cell edge of 250 pm. Calculate the density if 300 g of this element contain 2 1024 atoms. 13. H2O2 : 1.0 104 K log k = 14.2 T - 200 , Ea k ( : R = 8.314 J K 1 mol 1) The rate constant for the first order decomposition of H2O2 is given by the following equation : log k = 14.2 1.0 104 K T Calculate Ea for this reaction and rate constant k if its half-life period be 200 minutes. (Given : R = 8.314 J K 1 mol 1) 14. (iii) MgCl2 AlCl3 ? ? (i) Differentiate between adsorbtion and absorption. (ii) Out of MgCl2 and AlCl3, which one is more effective in causing coagulation of negatively charged sol and why ? (i) (ii) (iii) Out of sulphur sol and proteins, which one forms multimolecular colloids ? 15. (iii) Al Al2O3 NaOH ? ? (i) Name the method of refining of metals such as Germanium. (ii) In the extraction of Al, impure Al2O3 is dissolved in conc. NaOH to form sodium aluminate and leaving impurities behind. What is the name of this process ? (i) (ii) (iii) What is the role of coke in the extraction of iron from its oxides ? 56/1/1/D 5 [P.T.O. 16. 298 K e.m.f : 2Cr(s) + 3Fe2+(0.1M) 2Cr3+(0.01M) + 3 Fe(s) : E (Cr3+ | Cr) = 0.74V E (Fe2+ | Fe) = 0.44 V Calculate e.m.f of the following cell at 298 K : 2Cr(s) + 3Fe2+(0.1M) 2Cr3+(0.01M) + 3 Fe(s) Given : E (Cr3+ | Cr) = 0.74 V E (Fe2+ | Fe) = 0.44 V 17. : (i) Mn +7 , +4 (ii) (iii) Give reasons : (i) Mn shows the highest oxidation state of +7 with oxygen but with fluorine it shows the highest oxidation state of +4. (ii) Transition metals show variable oxidation states. (iii) Actinoids show irregularities in their electronic configurations. 18. : (i) (ii) CH3 | CH3 C O CH3 + HI | C H3 B2H6 CH3 CH = CH2 (i) (ii) 3H2O2/OH (iii) C6H5 OH (i) aq.NaOH (ii) CO2, H+ Write the main product(s) in each of the following reactions : (i) (ii) CH3 | CH3 C O CH3 + HI | C H3 B2H6 CH3 CH = CH2 (i) (ii) 3H2O2/OH (iii) C6H5 OH 56/1/1/D (i) aq. NaOH (ii) CO2, H+ 6 19. A, B C : (i) Br2/aq.KOH NaNO2 + HCl KI C6H5 CONH2 A B C 0-5 C (ii) KCN LiAlH4 CHCl3 + alc.KOH CH3 Cl A B C Write the structures of A, B and C in the following : 20. (i) Br2/aq. KOH NaNO2 + HCl KI C6H5 CONH2 A B C 0-5 C (ii) KCN LiAlH4 CHCl3 + alc. KOH CH3 Cl A B C (i) t- ? (ii) : [NH (CH2)6 NH CO (CH2)4 CO ]n (iii) : , , -S (i) What is the role of t-butyl peroxide in the polymerization of ethene ? (ii) Identify the monomers in the following polymer : [NH (CH2)6 NH CO (CH2)4 CO ]n (iii) Arrange the following polymers in the increasing order of their intermolecular forces : Polystyrene, Terylene, Buna-S OR Write the mechanism of free radical polymerization of ethene. 56/1/1/D 7 [P.T.O. 21. (iii) - C ? ? (i) Write the name of two monosaccharides obtained on hydrolysis of lactose sugar. (ii) Why Vitamin C cannot be stored in our body ? (i) (ii) (iii) What is the difference between a nucleoside and nucleotide ? 22. (b) [Fe(CN)6]3 , ( . . : Fe = 26) [Pt(en)2Cl2]2+ (a) For the complex [Fe(CN)6]3 , write the hybridization type, magnetic character (a) and spin nature of the complex. (At. number : Fe = 26). (b) Draw one of the geometrical isomers of the complex [Pt(en)2Cl2]2+ which is optically active. 23. . . . - , . : (i) ( ) ? (ii) ? (iii) ? Due to hectic and busy schedule, Mr. Angad made his life full of tensions and anxiety. He started taking sleeping pills to overcome the depression without consulting the doctor. Mr. Deepak, a close friend of Mr. Angad, advised him to stop taking sleeping pills and suggested to change his lifestyle by doing Yoga, meditation and some physical exercise. Mr. Angad followed his friend s advice and after few days he started feeling better. After reading the above passage, answer the following : (i) What are the values (at least two) displayed by Mr. Deepak ? (ii) Why is it not advisable to take sleeping pills without consulting doctor ? (iii) What are tanquilizers ? Give two examples. 56/1/1/D 8 24. (a) (b) : (i) (ii) PCl5 : (iii) HOF (i) BrF5 (ii) XeF4 (i) F2 Cl2 : , - (ii) H2SO4 (iii) : (a) (a) H3PO3, H3PO4, H3PO2 ( ) (b) NH3, PH3, AsH3, SbH3, BiH3 ( ) Account for the following : (i) Ozone is thermodynamically unstable. (ii) Solid PCl5 is ionic in nature. (iii) Fluorine forms only one oxoacid HOF. (b) Draw the structure of (i) BrF5 (ii) XeF4 OR (i) Compare the oxidizing action of F2 and Cl2 by considering parameters such as bond dissociation enthalpy, electron gain enthalpy and hydration enthalpy. (ii) Write the conditions to maximize the yield of H2SO4 by contact process. (iii) Arrange the following in the increasing order of property mentioned : 56/1/1/D (a) H3PO3, H3PO4, H3PO2 (Reducing character) (b) NH3, PH3, AsH3, SbH3, BiH3 (Base strength) 9 [P.T.O. 25. (a) A, B, C, D E : CH3COCl C6H6 Anhyd.AlCl3 A Zn Hg/conc.HCl (i) KMnO4 KOH, B C (ii) H3O+ NaOI D+E (a) (b) (c) Cl CH2 COOH (d) : F-CH2-COOH pKa ? CH3 CH = CH CH2CN (i) DIBAL-H (ii) H2O (e) (a) Write the structures of A, B, C, D and E in the following reactions : CH3COCl Zn Hg/conc.HCl (i) KMnO4 KOH, C6H6 A B C Anhyd.AlCl3 (ii) H3O+ NaOI D+E OR (a) Write the chemical equation for the reaction involved in Cannizzaro reaction. (b) Draw the structure of the semicarbazone of ethanal. (c) Why pKa of F-CH2-COOH is lower than that of Cl CH2 COOH ? (d) Write the product in the following reaction : DIBAL-H CH3 CH = CH CH2CN (i) (ii) H2O (e) 56/1/1/D How can you distinguish between propanal and propanone ? 10 26. (a) 50 g 1.9 g MgCl2 (M = 95 g mol 1) , MgCl2 : ( Kf = 1.86 K kg mol 1) (b) (i) 1 M 2 M ? (ii) ? (a) 100 g CS2, 2.56 g , (Sx) (CS2 (b) (a) 0.383 K Kf = 3.83 K kg mol 1, . . = 32 g mol 1) 0.9% , (i) 1.2% ? (ii) 0.4% ? Calculate the freezing point of solution when 1.9 g of MgCl2(M=95 g mol 1) was dissolved in 50 g of water, assuming MgCl2 undergoes complete ionization. (Kf for water = 1.86 K kg mol 1) (b) (i) Out of 1 M glucose and 2 M glucose, which one has a higher boiling point and why ? (ii) What happens when the external pressure applied becomes more than the osmotic pressure of solution ? OR (a) When 2.56 g of sulphur was dissolved in 100 g of CS2, the freezing point lowered by 0.383 K. Calculate the formula of sulphur (Sx). (Kf for CS2 = 3.83 K kg mol 1, Atomic mass of Sulphur = 32 g mol 1] (b) 56/1/1/D Blood cells are isotonic with 0.9% sodium chloride solution. What happens if we place blood cells in a solution containing (i) 1.2% sodium chloride solution ? (ii) 0.4% sodium chloride solution ? 11 [P.T.O. 56/1/1/D 12

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