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GOLDCREST HIGH-LATUR ON THE WINGS OF EXCELLENCE PRELIM-02 SUBJECT:-CHEMISTRY (PAPER-01) TIME:3 HOURS DATE:-19.01.17 GRADE: XII MARKS:70 General Instructions (Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time) --------------------------------------------------------------------------------------------------------------------Answer all questions in Part I and six questions from Part II, choosing two questions from Section A, two from Section B and two from Section C. 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 [ ] 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 the problems, use the following Gas constant R = 1.987 cal deg mol- = 8.314 J K- mol= 0.0821 L atm K- mol- 1 L atm = 1dm atm = 101.3J Avogadro s number = 6.023 x 10 -1 1 1 1 1 3 1 23 PART- I (20Marks) (Answer all questions) Question-01 (a)Fill in the blanks by choosing the appropriate word/words from those given in the brackets: (acetaldehyde, salt solution ,0.68, R,formaldehyde,buffer solution ,0.524,i, calcium formate ,50 minutes,below,45 minutes,0.74,vant t hoff factor,Raoult s Law,weak,strong,increases,decreases,positive negative,above) [5] (i) The solution obtained by mixing appropriate amount of ------------ base and its salt with strong acid is called-------(ii) An aqueous solution of glucose boils ----------100 oC and freezes-----------0 oC . (iii) The ratio of the observed value of a colligative property to the normal value of the same property is termed as -----and is represented by letter ---------(iv) When a mixture of calcium acetate and ---------is subjected to dry distillation----------is obtained. (v) A ------- catalyst increases the rate of chemical reaction while a negative catalyst ----------- the rate of reaction. (b)Complete the following statements by selecting the correct alternatives from the choices given: [5] (i)A saturated solution of Ag2CrO4 is 2 x 10-4 moles/litre.Its solubility is: (1)4.4 x 10-8 (2)3.2 x 10 -11 (3) 2.8 x10-9 (4) 5.6 x 10 -12 (ii)A molecule contains atoms X and Y so that X occurs at the corners of the cube while Y at the face centres.The formula of the molecule can be (1) XY3 (2) XY (3) X 2Y (4)XY2 (iii) 15 moles of H2 and 5.2 moles of I2 are mixed and allowed to attain equilibrium at 500 oC. At equilibrium the concentration of HI is found to be 10 moles. The equilibrium constant for the formation HI is (1) 50 (2) 15 (3) 100 (4) 25 (iv)Glucose gives silver mirror test with Tollen s reagent. It shows the presence of : (1) alcoholic group (2) Ketonic group (3) Aldehydic group (4) acidic group (v)In the formation of K4[Fe(CN)6],the hybridization involved is : (1)dsp2 (2)d2sp3 (3)sp3d2 (4)sp3 (c) Answer the following : (i)Why Fe2+ has smaller radius than Mn2+? (ii)Write the Nernst equation for the following cell reaction: Zn(s) / Zn2+(aq) // Cu2+(aq) / Cu(s). (iii) Draw the structure of isomers for the molecular formula C 3H6Cl2 which can exhibit optical isomerism. (iv) What are the products formed when phenol and nitrobenzene are treated separately with a mixture of conc.sulphuric acid and conc nitric acid? (v) How will you prepare 2 methyl propane-2-ol from methyl magnesium bromide? Give balanced equation [5] (d) Match the following: [5] (i) Specific conductivity (a)Argentite (ii)Froth flotation process (b) Thermosetting plastics (iii)Aniline (c) Bidentate Ligand (iv)Bakelite (d) Ohm -1cm-1 (v) Ethylene diamine (e) Diazotisation PART II (50 Marks) Answer six questions choosing two from Section A, two from Section B and two from Section C. SECTION A Answer any two questions. Question-02 (a)(i) Calculate the mass of a non-volatile (molar mass 60) that needs to be dissolved in 100 gm of water in order to decrease the vapour pressure of water by 25 %.What will be the molality of the solution? [2] (ii) Prove that the time required for the completion of 75% of a reaction of first order is twice the time required for 50% completion of the reaction. [2] (b)(i) Explain the following: (i) Common salt is purified by bubbling hydrogen chloride gas through its solution. (ii) Dissociation of H2S is suppressed in acidic medium. [2] (ii) Kc for the reaction H2(g) + I2(g) 2HI(g)+ I2(g) 2HI(g) is 54.8 at 700 K. If 0.5 mole/litre of HI(g) is present at equilibrium at 700K,what are the concentration of H2(g) and I2(g) assuming that we initially started with HI(g) and allowed it to reach equilibrium at 700K? [2] (iii) What is Schottky defect in solid crystal? The radius of Na + ion is 95 pm and that of Cl- ion is 181 pm .Predict the coordination number of Na+ ion . [2] Question-03 (a) (i) The standard reduction potentials of cadmium and silver electrodes are -0.04V and 0.08 V respectively.(i) Represent the cell ,where the reaction Cd + 2Ag+ Cd2 + 2Ag (ii)calculate the standard emf of the cell.(iii) calculate the emf of the if 0.01 M soln. each of Cd2+ and Ag+ are used. (iv) Is the free energy change of the reaction taking place in the above reaction positive or negative? [4] (ii) An element crystallizes in bcc structure. If edge length of cell is 1.469 x 10 -8 cm and density 19.3g/cm 3, then calculate the atomic mass of the element [2] (iii) The experimental data for the reaction : 2A + B 2 2AB, are as follows. Write probable rate expression. [A] mol/L 1 0.5 0.5 1.0 [B2] mol/L 1 Initial rate (mol L 1 sec 1) 1.6 10 4 3.2 10 4 3.2 10 4 0.5 1.0 1.0 [2] (b) A conventional method of representing a Daniel cell is : Zn (s) | Zn 2+ (1M) || Cu2+ (1M) | Cu (s). (i) Draw a diagram of the cell and mark anode and cathode as current is drawn from the cell. (ii) Write the reactions taking place at the cathode and the anode during the operation of Daniel cell. [2] Question-04 (a)(i)Calculate the hydrolysis constant, degree of hydrolysis, P H value and the [OH-] in 0.1 M NH4Cl solution . (KNH4OH=1.75 x 10-5.Kw=10-14) (ii) The solubility product of silver chloride is 1.0 x 10 -10 at 250C. Calculate the solubility of silver chloride in: (i) Pure water (ii) 0.2 M sodium chloride [3] [2] (b) (i)The Haber s process the manufacture of ammonia is based on the equilibrium: N 2(g) + H2(g) 2NH3(g).How is the composition of the equilibrium is affected by (i) a change in temperature (ii) a change in pressure (iii) a change in concentration of one of the reactants. [3] (c) All Arrhenius acids are Bronsted-Lowry acids but all Arrhenius bases are not Bronsted-Lowry bases. Justify this statement with example [2] SECTION B Answer any two questions Question-05 (a) Give the IUPAC name for the following: (i) Na 3[AlF6] (ii) [Co(NH3)6Cl3 (b)For the complex ion of [Fe (CN)6]3- (i) Show the hybridization diagramatically (ii)Is it an inner orbital complex or outer orbital complex? (iii) State its magnetic properties [2] [3] Question-06 (a) (i)Describe the manufacture of ozone by Siemen s Ozonizer. How is pure ozone recovered from the products? [2] (ii)Give the balanced reaction for the reaction: (i)Chlorine with hot concentrated caustic soda (ii) Sulphur dioxide with acidified potassium dichromate. (iii) Zinc is added to sodium argentocyanide solution. [3] Question-07 (a)Give reasons for the following: (i) SF 6 exists but OF6 does not, though both oxygen and sulphur belong to Group 16 in the Periodic table. (ii)Zn2+ compounds are white in colour but Cu2+ compounds are coloured ,though both zinc and copper are transition metals . [3] (b) (i) To which class of compounds does IF7 belong? Draw the structure of the molecule. (ii)Give the balanced chemical equation for the preparation of silver nitrate in the laboratory. [2] SECTION C Answer any two questions Question-08 (a) Give balanced reaction for the following named reaction:(i)Sandmeyer s reaction (ii)Aldol Condensation (iii)Wolff-Kishner reduction (iv) Williamson synthesis (v) Fridel- crafts Reaction [5] (b) How will you convert the following:(i)Methyl chloride to acetic acid (ii) Benzene to benzoic acid (iii)Ethanol to acetone [3] (c)Give one chemical test to distinguish the following pairs of compounds:(i) 1 propanol and 2 propanol and benzoic acid. (ii) oxalic acid [2] Question-09 (a) Give balanced equations for the following:(i) Glycerol is heated with oxalic acid at 110 oC. (ii) Acetamide is heated with sodium hydroxide. (iii) Acetone reacts with hydrogen in presence of heated copper. [3] (b) Identify A to F: A -----LiAlH4 C2H5OH------PBr3 B----KCN C-----D C3H7NH2 -----HNO2 E ----K2Cr2O7 F [3] (c) An organic compound X has molecular formula C 7H6O.When X is treated with NaOH followed by acid hydrolysis, it gives two products Y and Z. When Y is oxidized it gives X. When X and Z are each treated with PCl 5 separately, they give two different organic compounds S and W. (i) Identify X,Y,Z,S and W. (ii) Give the chemical reactions when X is treated with NaOH and name the reaction [4] Question-10 (a)(i)What are thermoplastics and thermosetting plastics? Mention one example of each kind. [2] (ii) Give one example of a fibrous protein. Name the final product when protein is hydrolysed What is denaturation of protein? [2] (iii)At 110oC oxalic acid reacts with an organic compound A with molecular C 3H8O3 to monocarboxylic acid B .B gives silver mirror with Tollens s reagent and reduces acidified potassium permanganate solution.Identify A and B and give reaction of B with acidified KMnO4 solution. [2] (b)(i) What is Biuret reaction(test) and Hinsberg s test? (c) Convert the following: (i)Fructose to osazone [2] (ii) Phenol to salicyclic acid ________________________________ END ____________________________________ [2] - SECTION B Answer any two questions Question-05 SECTION C Answer any two questions. Question-08 ________________________________ END ____________________________________ ________________________________ END ____________________________________
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