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SAINT LAWRENCE SCHOOL, TENTOLOI HALF YEARLY EXAMINATION- 2020 CLASS- IX CHEMISTRY F M- 80 SECTION- I (ANSWER ALL QUESTIONS FROM SECTION- I) 1. a) b) c) d) e) 2. a) b) c) d) e) 3. a) 4. a) b) 5. a) b) c) d) e) 6. a) b) c) d) e) f) g) h) i) j) Give reason for the following. (5) Many elements have fractional atomic masses. Symbol S is used for sulphur and Na is used for sodium. Table salt become sticky on exposure dur2ing rainy season. Fused CaCl2 is used in a desiccator. The first period of modern periodic table has only two elements whereas second period has eight elements. Write chemical formula for the following. (5) Potassium acetate Sodium bromate Chromium thiosulphate Barium oxalate Bismuth nitrite Find valency of the Na,S,Au in the following compounds. (3) Na2O b) SO3 c) AuCl3 Balance the chemical equations by hit and trial method. (2) KOH + Cl2- KCl + KClO3 + H2O Al4C3 + H2O- Al(OH)3 + CH4 Answer the following. (5) Name the lightest alkali metals. Name the group that contains elements beryllium and magnesium. Name the last members of period 2 and 3. Nature of oxides formed by the elements on left hand side of periodic table. Name an alkali metal in period 2. Answer the following. (20) What is the atomic number of an element X with 15 protons and 16 neutrons? Write electronic configuration of X. Calculate the molecular mass of Na2SO4.10H2O. (Na=23,S=32,O=16,H=1) How solubility of KNO3 and CaSO4 in water is affected by temperature? Valency of a metal is 2. Write the formula of its bisulphide and hydride. Assign position to the elements with atomic number 9 and 19 in the periodic table. Name the elements present in, Period 3 and group 2 Period 2 and group 13 Differentiate between thermal decomposition and thermal dissociation( with examples) Give one test to prove that the given liquid is water. ( write reaction) Give the chemical name and formulae of nitre and quick lime. What do 35,17,-, and Cl mean in 3517Cl-? SECTION II 7. 8. a) b) c) d) e) (ANSWER ANY FOUR QUESTIONS) a) Write chemical names of the following compounds. (4+3+2+1) NaIO, K2PbO2, NH4CNS, Na3[Fe(CN)6] b) Calculate the total percentage of oxygen in FeSO4.7H2O. ( Fe=56, S=32, O=16, H=1 ) c) Write balanced chemical equation for the following two reactions. Phosphorus burns in air to form phosphorus pentoxide Carbon dioxide passed through lime water to form calcium carbonate and water. d) Why formula of manganese(IV) oxide is MnO2 but not MnO4? (2+2+2+3+1) Heating of NaNO3 is a simultaneous change, explain.(with reaction) Glauber s salt exhibits anomalous solubility, explain. Give example of a photochemical reaction and an endothermic reaction.(Give reactions) What mass of KNO3 is required to prepare 70g of KNO3 from its saturated solution at 800C? Its solubility at 800C is 150g and at 200C is 90g. Give the name and formula of a crystalline salt having two molecules of water. 9. (3+3+4) a) Atomic number of some elements of modern periodic table are 4, 9, 14, 19, 20 Answer the following three questions. i) Name the element that has one electron in the outermost shell and write its electronic configuration. ii) Name the two elements that belong to the same group. iii) Name the two elements that belong to the same period. b) Write the advantages of long form periodic table over Mendeleev s periodic table. c) What determines which element will be the first and which will be the last in a period of the periodic table? d) Why the properties of elements are repeated after 2,8,18 and 32 elements? e) If an element is in group 17, it is likely to be metallic or nonmetallic in character. f) An element is having three shells and four valence electrons, name the element. 10. (3+3+2+2) a) Identify the type of bonding and draw orbit structural diagram for K2O and N2. b) Calculate the relative atomic mass of copper which consists of 69% of 63Cu and 39% of 65 Cu isotopes. c) State the meaning of octet and name two elements which do not acquire this configuration during bond formation. d) State Bohr-Bury concept of electronic configuration. 11. (3+2+2+3) a) Why magnesium gains weight on burning? b) When ammonium nitrate dissolves in water,it becomes cold,give reason. c) When water is added to concentrated H2SO4,heat is produced. Why this change is a physical change? d) How will you find whether energy is released or absorbed during a chemical reaction? e) Differentiate between hydrated substance and anhydrous substance. f) Water is a universal solvent,explain.
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