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Class 12 ISC Board Exam 2018 : Chemistry

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Suresh Balan
SDR School, Tuticorin

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CHEMISTRY PAPER 1 (THEORY) (Three Hours) Answer to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. All questions are compulsory Question 1 is of twenty marks having four sub parts all of which are compulsory. Question numbers 2 to 8 carry 2 marks with two questions having internal choice. Question numbers 9 to 15 carry 3 marks with two questions having internal choice. Question numbers 16 to 18 carry 5 marks each. Each question has an internal choice. 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 data: Gas constant R = 1.987 cal deg-1 mol-1 = 8.314 K-1 mol-1 : Avogadro s number = 6.023 X 1023 PART I (20 Marks) (Answer ALL questions) Question: 1 a) Complete the following statements by selecting the correct alternatives from the choices given: [4 X 1] (i) Which of the metal is leached by cyanide process? (a) Ag (ii) (b) Hg2O (c) Hg(OH)2 (d) HgCl2 (b) + 4 (c) + 7 (d) + 6 (b) Antiseptic (c) Insecticide DDT is used as: (a) Anaesthetic b) (d) Cu In KMnO4 oxidation number of Mn is: (a) +2 (iv) (c) Al Tailing of Mercury is due to the formation of: (a) HgO (iii) (b) Na Fill in the blanks: (d) Refrigerant [4 X 1] (i) The well known refrigerant Freon has the structure ____. (ii) IUPAC name of picric acid ______. (iii) The common name of 1,2,3 trihydroxy-benzene is ________. (iv) Oxygenated water is _____________. Page 1 of 5 c) Match the following: Column I Haber s process Contact process Vegetable oil or ghee Sandmeyar reaction (A) (B) (C) (D) d) [4 X 1] (i) (ii) (iii) (iv) Column II Cu2Cl2 Ni / H2 V2O5 Finally divided Iron Answer the following: (i) [4 X 2] On reaction with Cl2, phosphorus form two types of halides A and B. Halide A is yellowish white powder but halide B is a colourless oily liquid. Identify A and B and write the formula of their hydrolysis product. (ii) CoSO4Cl. 5 NH3 exists in two isomeric forms A and B. Isomer A reacts with AgNO3 to give white precipitate, but does not reacts with BaCl2. Isomer B gives white precipitate with BaCl2 but does not reacts with AgNO3. Identify A and B and write their structural formulae. (iii) Write the structure of the major organic product in each of the following reaction? a) H3C b) H3C H2 C H C H2 C H2 C NaI + Cl Acetone Heat CH3 + NaOH water Br (iv) Name the reagents used in the following reactions. a) Oxidation of primary alcohol to carboxylic acid. b) Dehydration of propan-2-ol to propene. c) PART II Question 2 [2] Why is limestone added to the ore in the metallurgy of iron? OR Zinc acts as reducing agent in the extraction of silver. Comment. Page 2 of 5 Question 3 [2] SF6 exists but OF6 does not, though both oxygen and sulphur belong to the same group in the periodic table. Question 4 [2] Assign reason for each of the following: i. Transition metals generally form coloured compounds. ii. Manganese exhibits the highest oxidation state of +7 among the 3d series of transition elements. Question 5 [2] Draw the cis and trans isomers of [Pt Cl2 (NH3)2 ]. Question 6 [2] Write the chemical equation for the preparation of phenol from chlorobenzene. Question 7 [2] Write the structure of the major organic product in each of the following reactions. i. Reaction of n-propanol with thionyl chloride. ii. Action of KI with benzene diazonium chloride. OR i. Reaction of but-1-ene with HBr in the presence of peroxide. ii. Reaction between sodium phenoxide and ethyl chloride. Question 8 [2] Using IUPAC norms write the systematic names of the following: i. K2 [ Ni (CN)4 ] ii. [ Co (NH3)5 Cl ] Cl2 Question 9 [3] Reason out the following in the metallurgy process with the relevant equation. i. ii. iii. Give an equation to show how zinc oxide is converted to zinc. What is the role of graphite rod in the electrometallurgy of aluminium? State the role of silica in the metallurgy of copper. Page 3 of 5 Question 10 [3] How is hydrogen peroxide prepared in the laboratory? OR What happens when hydrogen peroxide is added to acidified potassium permanganate solution? Question 11 [3] i. What are inner transition compounds? ii. Describe the atomic numbers present in Lanthanoids and Actinoids. iii. Describe which of the following atomic numbers are the atomic numbers of the inner transition elements : 29, 59, 74, 95, 102, 104. Question 12 [3] [ CoF6 ] 3- is a coordination complex ion. i. What is the coordination number of the complex? ii. What is the oxidation number of cobalt in the complex? iii. Sate the magnetic behaviour of the complex. Question 13 [3] Name the type of isomerism shown by the following pairs of coordination compounds. i. [PtCl2 (NH3)4] Br2 and [PtBr2 (NH3)4] Cl2 ii. [Cr (SCN) (H2O)5]2+ and [Cr (NCS) (H2O)5]2+ iii. [Cr (H2O)5 Cl] Cl2. H2O and [Cr (H2O)4 Cl2] Cl. 2H2O OR Name the type of isomerism shown by the following pairs of coordination compounds. i. [CoCl (H2O) (NH3)4] Cl2 and [CoCl2 (NH3)4] Cl. H2O ii. [Pt (NH3)4][Pt Cl6] and [Pt (NH3)4 Cl2][Pt Cl4] iii. [Co (NH3)5 NO2] Cl2 and [Co (NH3)5 ONO] Cl2 Question 14 [3] What happened when chlorobenzene undergoes Nitration, Sulphonation and Brominations? Page 4 of 5 Question 15 [3] Describe Williamson s ether synthesis. Question 16 i. Write chemical reactions taking place in the extraction of zinc from zinc blende. [3] ii. Describe the reactions of F2 and Cl2 with water. [2] OR iii. iv. Justify the placement of O, S, Se, Te and Po in the same group of the periodic table in terms of electronic configuration, oxidation state and hydride formation. [3] How XeO3 and XeO4 are prepared? [2] . Question 17 For the complex ion of [ Fe (CN)6 ] 3-. i. ii. iii. iv. Show the hybridization diagrammatically. Is it an inner orbital complex or an outer orbital complex? State is Magnetic Property. Draw the structure of the anionic complex. [2] [1] [1] [1] OR For the complex ion of [ Fe (H2O)6 ] 2+. i. ii. iii. iv. Show the hybridization diagrammatically. Is it an inner orbital complex or an outer orbital complex? State is Magnetic Property. Draw the structure of the anionic complex. [2] [1] [1] [1] Question 18 i. ii. iii. iv. i. ii. iii. iv. A hydrocarbon C6H12 does not reacts with chlorine in dark but gives a single monochloro compound C6H11Cl in bright sunlight. Identify the hydrocarbon. [2] Convert Benzene to BHC. [1] Reaction of ethyl bromide with alcoholic silver cyanide. [1] What will be the product formed when chlorobenzene is heated with sodium metal in the presence of dry ether? [1] OR Reaction of ethanol with acetyl chloride. [1] Chlorine is passed through diethyl ether. [1] What happened when phenol reacts with potassium persulphate (pH = 10) [1] Explain briefly about oxymercuration of 1-butene with equation. [2] Prepared by B.SURESH M.Sc., B.Ed., PG ASSISTANT IN CHEMISTRY (ISC / ICSE) mail id: resh986@gmail.com Ph: 7339317695 Chapters Covered Unit 6,7,8,9,10,11,12 Page 5 of 5

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