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CBSE Class 12 Pre Board 2021 : Chemistry - Set 1 (CBSE Gulf Sahodaya Qatar Chapter, Doha)

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Pre Board Exam, 2020-21 Chemistry, (043) Theory Class XII Time: 3 hr MM: 70 General Instructions: Read the following instructions carefully. a) There are 33 questions in this question paper. All questions are compulsory. b) Section A: Q. No. 1 to 16 are objective type questions. Q. No. 1 and 2 are passage based questions carrying 4 marks each while Q. No. 3 to 16 carry 1 mark each. c) Section B: Q. No. 17 to 25 are short answer questions and carry 2 marks each. d) Section C: Q. No. 26 to 30 are short answer questions and carry 3 marks each. e) Section D: Q. No. 31 to 33 are long answer questions carrying 5 marks each. f) There is no overall choice. However, internal choices have been provided. g) Use of calculators and log tables is not permitted. SECTION A (Objective Type) 1. Read the passage given below and answer the following questions: Solids may be classified as amorphous and crystalline. Amorphous solids are isotropic whereas crystalline solids are anisotropic. Solids can also be classified on the basis of type of forces of attraction as ionic, covalent, metallic and molecular solids. Unit cells represent crystal lattice. Types of cubic crystal lattice-bcc, fcc and simple cubic. The packing efficiency of fcc is 74%, bcc is 68% and simple cubic packing is 52%. The vacant sites are called voids, tetrahedral and octahedral voids are being most common. There are defects in crystal lattice, point defects like Frenkel and Schottky. Non-stoichiometric defects are metal excess type, metal deficient type and impurity defects. These defects affect the properties of solids. i. Name the vacancy defect which reduces the density of a crystal. a. Frenkel defect. b. Schottky defect. c. Impurity defect. d. All the above. ii. The crystal which show both Frenkel as well as Schottky defect is a. AgBr b. ZnS c. NaCl d. CsBr 1 4x1

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