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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-?
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