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ISC Class XII Prelims 2020 : Chemistry (The Shri Ram School (TSRS), Moulsari, DLF Phase III, Gurgaon)

9 pages, 86 questions, 13 questions with responses, 14 total responses,

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The Shri Ram School Moulsari Campus Second Term Examinations-2019-20 Class: XII Chemistry Time: 3 hrs M.M.: 70 (Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time) All questions are compulsory Question 1 is of twenty marks having four sub parts all of which are compulsory. Questions 2 to 8 carry 2Marks each with two question having internal choice. Question 9 to 15 carry 3Marks each with two question having internal choice. Question 16 to 18 carry 5Marks each with all question having internal choice. 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 data: Gas constant R = 1.987 cal deg-1 mol-1 = 8.314 J K-1 mol-1 = 0.0821 L atm K-1 mol-1 ,1 L atm = 1 dm3atm = 101.3J There are nine printed sides to the paper. Answer all questions Question 1 a. Fill in the blanks with appropriate words/phrases: [4] [Conductivity, equivalent weight, electrochemical equivalent, 6, 8, 12, 4, C6H5NO2, C6H5OH, C6H5NH2,C6H5N2+BF4- ,C6H5F, increases, remains same, C6H5F, Phenol, urea, formaldehyde, butadiene, melamine, terepthalic acid,decreases] i. The coordination numbers of hcp is . and that of an octahedron void is .. Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 1 ii. iii. and .. are the monomers of bakelite. Density of a crystal due to Schottky defect and . due to Frenkel defect. iv. b. Choose the correct option: i. [4] Three elements X, Y and Z crystallise in a cubic solid with X at corners, Y at body centre and Z at the face centres of the cube, then the formula of the solid is A. XYZ B. X3YZ C. XYZ3 D. XY3Z ii. Which properties are typical of d-block elements? I. complex ion formation II. catalytic behavior III. colourless compounds A. I and II only B. I and III only C. II and III only D. I, II and III iii. When both positive and negative ions of a salt are complex ions and the two isomers differs in the distribution of ligands in the cation and the anion; it is a type of: A. B. C. D. Optical isomerism Geometrical isomerism Coordination isomerism Linkage isomerism iv. The metal which is refined by Mond s process is A. B. C. D. Iron Zirconium Nickel Titanium Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 2 c. Match the following: [4] i. Acetaldehyde ii. Optical activity iii. Polyester iv. Milk a) b) c) d) e) Addition polymer Condensation polymer emulsion lactic acid Iodoform d) Answer the following questions: i. ii. [8] Explain the following; [1+1] 2+ 3+ 1. Cr is reducing agent and Mn an oxidizing agent although both have d4 configuration? 2. LiCl heated in excess of Li vapours appears pink in colour . Write the coordination number and oxidation state of Platinum in the complex [Pt (en)2Cl2]. [2] iii. Calculate the mass of ascorbic acid (Vitamin C, C6H8O6) to be dissolved in 75 g of acetic acid to lower its melting point by 1.5 C. (Kf = 3.9 K kg mol 1) [2] [Atomic Masses; C=12,H=1,O=16] iv. Covert; Ethanol to 3-Hydroxybutanal [2] Question 2 [2] Calculate the half-life of a first-order reaction whose rate constant is 200 s 1. Question 3 [2] An element has a body centred cubic (bcc) structure with a cell edge of 288 pm. The density of the element is 7.2 g/cm3. How many atoms are there in 208 g of the element? OR Chromium crystallises in BCC structure. If its atomic diameter is 245 pm, find its density. [ Atomic mass of Cr = 52 amu and NA = 6.02 1023 mol 1.] Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 3 Question 4 [1+1] What happens when ; (a) Phenol reacts with Br2 in CS2 at 273 K. (b) Phenol reacts with conc. HNO3. Give only balanced chemical equations. Question 5 [2] Calculate the equilibrium constant for the following reaction at 298 K. OR Following reaction takes place in the cell: Calculate G of the reaction. [Given E (Zn2+/Zn) = -0.76V, E (Ag+/Ag) = 0.80 V, 1 F = 96,500 C mol-1] Question 6 Complete and balance the following equations: [2] Question 7 [2] What type of semiconductor is obtained when: (i) Ge is doped with In (ii) Si is doped with P Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 4 Question 8 [2] Draw the structures of monomer(s) used to obtain the following polymers : (a) Nylon-6,6 (b) PVC Question 9 [3] The following reaction is a single step reversible reaction. The energy of activation for the forward reaction is 38.9 kJ and that of the backward reaction is 51.8kJ. Draw the energy level diagram indicating . Question 10 [1+2] a) Which type of linkage is present in the primary structure of protein? b) What happens when D-glucose is treated with HI/ Heat and Conc.HNO3? Give only equations for the chemical reactions. Question 11 [3] Identify A, B and C: Question12 a) Equi-molar solution of aluminum nitrate, magnesium nitrate and sodium chloride are added to equi-molar solution of negatively charged colloidal solution separately in three different beakers. Which electrolyte shall be more efficient for coagulation of negatively charged colloidal solution? Justify your answer and state the law involved. [1] Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 5 b) Explain auto catalysis with a suitable example. [1] c) Which colloidal property explains the blue colour of sky? Justify your answer. [1] Question 13 i. Aspirin helps in prevention of heart attack. Explain. [1] ii. Pick out the odd one from the following compounds based on their medicinal properties: [1] Luminal, Seconal, Phenacetin, Equanil iii. Why do antihistamines not affect the secretion of acid in the stomach?[1] OR Define the following terms with a suitable example of each: [3] (a) Tranquillisers (b) Antibiotics (c) Non-ionic detergents Question 14 a. Write balanced equations for the following: i. Acidified K2Cr2O7 with FeSO4 ii. KMnO4 with H2S in neutral medium [2] b. Outline the principle behind the Zone refining method [1] OR i. Why do transition metals exhibit higher enthalpies of atomisation? ii. What is lanthanoid contraction? Write its one consequence. iii. Name an element of the lanthanide series which is well known to show +4 oxidation state. Is it a strong oxidising agent or reducing agent? Question 15 Write the IUPAC names of the following compounds: [3] a. [Pt(NH3)2Cl(NO2)] b. K3[Al(C2O4)3] c. [Ni(CO)4] Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 6 Question 16 [3] (b) Explain the following Named reactions with the help of chemical equations [2] (i) Rosenmund s reduction (ii) Hell Volhard Zelinsky reaction OR a) Write the structures of the main products of the following reactions: (b)Give a simple chemical test to distinguish between Aniline and N,N -dimethylaniline. (c) Arrange the following in the increasing order of their pkb values: C6H5NH2, C2H5NH2, C6H5NHCH3 Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 7 [3] [1] [1] Question 17 (a) Name the chief ore of KMnO4. How is it extracted from its chief ore ? write balanced reactions with detailed explanation. [2] (b) What is the effect of increasing pH on K2Cr2O7 solution? [1] (c) Draw the structure of dichromate ion indicating the bond angles and bond lengths. [2] OR i. ii. Explain: (a) Perchloric acid is a stronger acid than sulphuric acid. (b) Noble gases are bigger in size than halogens of the respective period. (c) Solid PCl5 exhibits some ionic character. Draw the shape of XeO3. What is the hybridisation of Xe in XeO3? [3] [2] Question 18 a) How much weight of mercury will be produced by electrolysing 1.0 M Hg(NO3)2 solution with a current of 2 A for 3 hours [Atomic weight of Hg(NO3)2 = 200.6] [1] b) The conductivity of a solution containing 1 gram of anhydrous BaCl2 in 200 ml of water is found to be 0.0058 S cm-1. What shall be the molar conductance and equivalent conductance of the solution [Atomic weight of Ba=137 and Cl=35.5] [1.5] c) Define : standard hydrogen electrode. [1] d) Answer the following : [1.5] i. Which metal shall act as the strongest oxidizing agent between them? ii. Can we store Y(NO3)2 in a container made of X? Justify the answer. OR i. ii. Define Second law of Faraday. [1] Write the electrolyte, cathode, anode and the cell reaction when the battery is in use in case of a lead storage battery. [2] Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 8 iii. Calculate the emf of the following cell at 298 K : [2] [Given = E0cell = 2.71 V] Integrity Sensitivity T2/RR/Chem/2019-20 Pursuit of Excellence Pride in One s Heritage Page 9

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