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CBSE 12th Board Class 12 2020 : Chemistry

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Sifan Ali
Shri Ram Centennial School (SRCS), Dehradun

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SAMPLE PAPER XII 2019-20 CHEMISTRY Time : 3 hrs. M. Marks : 70 General Instructions (a) All questions are compulsory. (b) Section A: Q.no. 1 to 20 are very short answer questions (objective type) and carry 1 mark each. Section B: Q.no. 21 to 27 are short answer questions and carry 2 marks each. Section C: Q.no. 28 to 34 are long answer questions and carry 3 marks each. Section D: Q.no. 35 to 37 are also long answer questions and carry 5 marks each. There is no overall choice. However an internal choice has been provided in two questions of two marks, two questions of three marks and all the three questions of five marks weightage. You have to attempt only one of the choices in such questions. Use log tables if necessary, use of calculators is not allowed. (c) (d) (e) (f) (g) SECTION - A Read the given passage and answer the questions 1 to 5that follow: A Lead storage battery is the most important type of secondary cell having a lead anode and a grid of lead packed with PbO 2 as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL -1) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H2 SO4 falls to 1.139 g mL-1 . (20% H2SO4 by mass) (1) Write the reaction taking place at the cathode when the battery is in use. (2) How much electricity in terms of Faraday is required to carry out the reduction of one mole of PbO2? (3) What is the molarity of sulphuric acid before discharge? (4) Lead storage battery is considered a secondary cell. Why? (5) Write the products of electrolysis when dilute sulphuric acid is electrolysed using Platinum electrodes. Questions 6 to 10 are one word answers: (6) Name the substance used as depressant in the separation of two sulphide ores in Froth floatation method. (7) Name the unit formed by the attachment of a base to 1 position of sugar in a nucleoside. (8) Name the species formed when an aqueous solution of amino acid is dissolved in water? (9) What type of reaction occurs in the formation of Nylon 6,6 polymer?

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