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GOLDCREST HIGH-LATUR ON THE WINGS OF EXCELLENCE PRELIM-01 SUBJECT:-CHEMISTRY (PAPER-01) TIME:3 HOURS DATE:-04/01/2017 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 3 1 1 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: [5] (increases, formic acid, decreases, less, zero, small, paired, atoms, unpaired, ions,pentagonal bipyramidal, electrical, more, ethylamine, molecules, propanoic acid,methylamine, chemical) (i) An electrochemical cell converts ________ energy to _________ energy. (ii) The crystal of graphite is made up of ______________ while that of sodium chloride is made up of ---------------- . (iii) Ethyl isocyanide, on hydrolysis with dilute sulphuric acid, gives ______________ and _________________ . (iv) The molar conductance of a solution _______________ with dilution, while its specific conductance _______________ with dilution. (v) The Van t Hoff factor of acetic acid solution is ____________than one and the value of normal colligative property is ____________ than the observed colligative property of this solution. (b)Complete the following statements by selecting the correct alternative from the choices given: [5] (i) The molal freezing point constant of water is 1.86 K Kg mol -1.Therefore, the freezing point of 0.1M NaCl solution in water is expected to be : (1)-1.86 oC (2) -0.372 oC (3) -0.186 oC (4) +0.372 oC -4 -1 (ii) For the first order reaction the rate constant for decomposition of N 2O5 is 6 x 10 Sec .The half life period for the decomposition in seconds is: (1)11.55 (2)115.5 (3)1155 (4) 1.155 (iii)When acetaldehyde is treated with Grignard reagent, followed by hydrolysis the product formed is : (1)Primary alcohol (2) Secondary alcohol (3) Carboxylic acid (4) Tertiary alcohol (iv) The geometry of XeF6 molecule and the hybridization of Xe in the molecule is : (1)Distorted octahedral and sp3 d3 (2) Square planar and sp3d2 (3)Pyramidal and sp3 (4) Octahedral and sp3d3 (v) In the complexs [Fe (CN)6]3- and [Pt(en)(H2O)2(NO2)(Cl)]2+ the respective oxidation numbers of central metal atoms are : (1) +3 and +4 (2) +6 and +4 (3)+6 and +3 (4) +3 and +3 (c) Answer the following questions: [5] (i) What is the [OH-] concentration of an acid whose pH is 5 at 25 C? O (ii) What happens when a nickel rod is dipped into a copper sulphate solution? Justify your answer. (iii) Write the equation for the preparation of acid anilide from aniline. (iv) Define Raoult s law for the elevation of boiling point of a solution. (v) An ionic compound is made up of A cations and B anions. If A cations are present at the alternate corners and B anion is present on the body of the diagonal, what is the formula of the ionic compound? (d)Match the following: [5] (i) Disaccharide (ii) Carbylamine (iii) Decron (a) Lucas reagent (b) Condensation polymer (c) Obnoxious smell (iv) Low spin complex,d2sp3 (d) Sucrose (v) Anhydrous ZnCl2 + conc .HCl (e) Hexaammine cobalt(III) ion 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) A solution containing 0.5 g KCl dissolves in 100 g of water and freezes at -0.24 oC.Calculate the degree of dissociation of the salt. Calculate the degree of dissociation of the salt. (K f for water =1.86 oC) Atomic.weight[K=39.Cl=35]. [2] (ii) 0.70 of an organic compound when dissolved in 32g of acetone produces an elevation of 0.25 oC in the boiling point. Calculate the molecular mass of organic compound (Kb for acetone= 1.72 K Kg mol-1). [2] (b)(i) Explain graphically how the rate of a reaction changes with every 10 oC rise in temperature [1] (ii) A substance decomposes by following first order kinetics.If 50% of the compound is decomposed in 120 minutes,how long will it take for 90% of the compound to decompose? [2] (c)(i)Define Frenkel defects of an ionic crystal. [1] (ii) Iron has an edge length 288 pm. Its density is 7.86gm/cm-3 .Find the type of cubic lattice to which the crystal belongs.(At.mass of iron =56) [2] Question-03 (a)(i)The equilibrium constant for the reaction : If .in a particular reaction, there are 0.25 mol L-1 of H2 and 0.06 mol L-1 of NH3 present ,calculate the concentration of N2 at equilibrium. [1] (ii)Calculate the value of E cell at 298K for the following cell. Al /Al3+(0.01M) // Sn+2 (0.015M)/Sn. Eo Al3+/Al= -1.66 volt and Eo Sn+2/Sn=0.14 volt [2] (iii) For a crystal of sodium chloride, state: (i)The type of lattice in which it crystallizes (ii)The coordination number of each sodium ion and chloride ion in the crystal lattice (iii)The number of sodium ions and chloride ions present in a unit cell of sodium chloride.(iv) The structural arrangement of the sodium chloride crystal. [2] (iv)Consider the following reaction: N2O4(g) + Heat = 2NO2(g) How is the composition of equilibrium mixture affected by: (i) a change in temperature (ii) a change in pressure (iii) a change in concentration of N 2O4 (iv) the removal of NO2 from the mixture. [2] (b) (i)The solubility product of silver chloride is 1.0 x 10-10 at 25oC .Calculate the solublity of silver chloride in (i)Pure water (ii) 0.2M sodium chloride solution [2] (ii)To precipitate group (III) cations NH 4Cl should be added to the solution before the addition of HH4OH.Explain why? [1] Question-04 (a)Explain the following:(i) The PH of a solution of sodium acetate is higher than that of pure water while the P H of a solution of zinc chloride is lower than that of pure water. (ii) Lead is precipitated as PbS while zinc is not precipitated when H2S gas is passed through acidic solutions of lead nitrate and zinc nitrate. [2] (iii) What is standard hydrogen electrode? 0 05 M NaOH solution offered a resistance of 31.60 ohm in a conductivity cell at 298 K. If the cell constant of the cell is 0 367 cm-1, calculate the molar conductivity of the NaOH solution. [3] (b)(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+ Cd 2 + 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? [3] (ii)State Kohlrausch s law and give its mathematical expression mentioning its terms involved. Give one point distinction between Piezo electricity and Pyro electricity. [2] SECTION B Answer any two questions Question-05 (a)Give the IUPAC name ,nature of bonding and draw the structures of (i)[Fe (CN)6]4- (ii)[CO(NH3)6]3+ [4] (iii)[COF6]3- (iv)[Fe(H2O)6]2+ (b)Write the formula of the following compounds: [1] (i) Triamminetriaquachromium(III)chloride Question-06 (ii) Potassiumhexacyanoferrate(III) (a) Name the types of isomerism shown by the following pairs of compounds: (i) [CoCl(H2O)(NH3)4]Cl2 and [2] [CoCl2(NH3)4]Cl.H2O (ii) [Pt(NH3)4][PtCl6] and [Pt(NH3)4Cl2][PtCl4] (b)Give the balanced chemical equation for the following: (i)Fluorine is passed through cold ,dilute NaOH soln. (iii) Sulphuric acid is treated with hydrogen sulphide. (ii)Hydrogen peroxide is treated with acidified KMnO 4. [3] Question-07 (a)(i)Draw the structure of xenon tetra fluoride molecule and state the hybridization of the central atom and the geometry of the molecule [1] (ii)Name the important ore of silver.Write all the steps and reactions involved in the Cyanide Process for the extraction of silver from its ore. [2] (b) Explain the following(i) Why do transition metal ions possess a great tendency to form complexes.(ii) The paramagnetic character in 3d transition series elements increases upto Mn and then decreases. [2] SECTION C Answer any two questions. Question-08 (a) Give balanced reaction for the following named reaction: (i) Reimer-Tiemann reaction (ii) Rosenmund reaction (iii) Hoffmann s degradation reaction (iv) Hell volhard Zelinsky(HVZ) reaction (v)Cannizaro reaction. [5] (b) Give one chemical test to distinguish between the following pairs of compounds (i)Ethylamine and diethylamine (ii) Acetaldehyde and benzaldehyde [2] (c) Identify the compound A B [3] C D E and F Question-09 (a) How can the following conversions be brought about: (i) Glycerol to formic acid (ii) Chlorobenzene to phenol (iii) Diethyl ether to ethanol (iv) phenol to aniline. [4] (b) (i)What is Isoelectric point? (ii) What is Biuret test? [2] (c) Name the monomers and the type of polymerization in each of the following polymers: [2] (i)Polyster (ii) Bakelite (iii) Teflon (iv) Nylon -6,6 (d) (i) The deficiency of which vitamin will cause the following diseases: [2] (i) Scurvy (ii) Haemorrhages Question-10 (a) An organic compound A with molecular formula C 7H8 on oxidation by chromylchloride in the presence of CCl 4 gives a compound B which gives positive tollen s test. The compound B on treatment with NaOH followed by acid hydrolysis gives two products C and D. C on oxidation gives B which on further oxidation gives D. The compound D on distillation with soda lime gives a hydrocarbon E. Below 60oC, concentrated nitric acid reacts with E in the presence of concentrated sulphuric acid forming a compound F. Identify the compounds A, B, C, D, E and F. [3] (b)What is Zwitter Ion? Represent the Zwitter ion of glycin [2] (c)How will you carry the following conversions: (i) Acetaldehyde to iso propyl alcohol.(ii) Acetone to acetone oxime (iii)Glucose to fructose (iv) Chloroform from ethyl alcohol (v) Methanol from Grignard s reagent. [5] ________________________________ END ____________________________________ ________________________________ END ____________________________________
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