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MADHUSTHALI VIDYAPEETH F.M 80 Time 2h Date : FIRST ASSESSMENT : 2019-2020 SUBJECT: CHEMISTRY CLASS- IX SECTION I (40 Marks) Attempt all questions from this section. Question 1 a) Choose the correct answer from the options given below: [5] i) Volume-temperature relationship is given by (Boyle s / Gay Lussacs / Dalton / Charles). ii) The valency of nitrogen in nitrogen dioxide (NO2) is (one/two/three/four). iii) The correct formula of aluminum oxide is (AlO3/AlO2/Al2O3). iv) In water, the hydrogen-to-oxygen mass ratio is (1:8/1:16/1:32/1:64). v) The absolute temperature value that corresponds to 27OC is (200K/300K/400K/246K). b) Fill in the blanks: [5] i) The temperature on the Kelvin scale at which molecular motion completely ceases is called ii) A catalyst either or the rate of a chemical change but itself remains at the end of the reaction. iii) Formula of Iron (III) carbonate is .. c) Write balanced chemical equation for each of the following: i) NaCl + AgNO3 [5] ii) Pb(NO3)2 + KI iii) CuCO3 iv) NH3 + O2 v) N2 + H2 d) Give one word or phrase for the following: [5] i) An artificial zeolite to remove hardness of water in large amounts. ii) A substance whose solubility increases rapidly with temperature. iii) A substance whose solubility increases and then decreases with rise in temperature. iv)A phenomenon where a compound loses its water of crystallization on exposure to dry air. v) Substances that absorb moisture from the atmosphere when they are exposed to it but not enough to form solutions. e) State one relevant observation for each of the following: i) Lead nitrate is strongly heated. ii) Chlorine water is exposed to sunlight. iii) Hydrogen peroxide is exposed to sunlight. iv) Barium chloride is added to sodium sulphate solution. v) Hydrated copper sulphate crystals are heated. [5] f) Give a reason for each of the following: i) Table salt becomes sticky on exposure to humid air during the rainy season. ii) Water is called as universal solvent. iii) fused CaCl2 or conc. H2SO4 is used as a drying agent. [5] This paper consists of three printed pages. iv) Gas fills completely the vessel in which it is kept. v) Gases exert pressure in all directions. g) Name the gas that is produced in each of the following: i) When zinc reacts with dilute sulphuric acid. ii) When carbon burns in oxygen. iii) When mercuric oxide is heated. iv)When electric current is passed through acidulated water. v) When potassium nitrate is heated. [5] h) Calculate: [5] i) The percentage composition of phosphorus in Calcium phosphate Ca3(PO4)2. ii) What temperature would be necessary to double the volume of a gas initially at S.T.P. if the pressure is decreased to 50%? SECTION II (40 Marks) Attempt any four questions from this section. Question 2 (a) (i) What do you understand by hard water? (ii) What is the cause of permanent hardness of water? (iii) State two methods to remove permanent hardness of water. [5] (b) Explain why: [5] (i) Boiled or distilled water taste flat. (ii) Ice at zero degree centigrade has a greater cooling effect than water at 0OC. (iii) Air dissolved in water contains a higher proportion of oxygen. (iv) If distilled water is kept in a sealed bottle for a long time, it leaves etchings on the surface of the glass. (v) Rain water does not leave behind concentric rings when boiled. Question 3 (a) (i) Explain the terms valency and variable valency. (ii) Write the chemical names of the following compounds: Ca3(PO4)2, Ag2SO3, Mg(HCO3)2 (b) (i) Define atomic mass unit. (ii) Calculate the relative molecular masses of : CuSO4.5H2O, (NH4)2CO3 [Atomic masses of: Cu=64, S=32, O=16, H=1, N=14, C=12] (iii) Write the empirical formula of: Acetylene (C2H2). [5] [5] Question 4 (a) (i) Define neutralization and precipitation reactions. (ii) Write a chemical reaction where the following changes are observed: 1. Gas is evolved. 2. Colour change is noticed. 3. Physical state is changed. [5] (b) Reactions can be classified as follows: Direct combination, decomposition, simple displacement, double decomposition, redox reactions. State which of the above types takes place in the reactions given below: [5] (i) Cl2 + 2KI 2KCl + I2 (ii) SO2 + 2H2O + Cl2 2HCl + H2SO4 (iii) 4HNO3 4NO2 + 2H2O + O2 2 (iv) 2Mg + O2 2MgO (v) AgNO3 + HCl AgCl + HNO3 Question 5 (a) (i) At 0OC and 760mm Hg pressure, a gas occupies a volume of 100cm3. The Kelvin temperature of the gas is increased by one-fifth, while the pressure is decreased by one-fifth times. Calculate the final volume of the gas. [5] (b) (i) State Charle s law. (ii) Give its graphical representation. (iii) A gas occupies 3 litres at 0OC. What volume will it occupy at 20OC, the pressure remaining constant? [5] Question 6 (a) (i) Explain solubility and solubility curves. [5] (ii) State differences between Hygroscopic substances, Drying agents and Dehydrating agents. (b) Write balanced chemical equations for the following reactions: [5] (i) Water is reacted with sodium. (ii) Steam is passed over red hot iron. (iii) Phosphorus combines with oxygen. (iv) Lead reacts with caustic soda. (v) Hydrogen reacts with nitrogen. Question 7 (a) (i) State two ways to remove temporary hardness. (ii) Name: 1. Greenish yellow gas. 2. Brown gas. 3. A substance is yellow when hot, but it turns white on cooling. [5] (b) (i) Classify as Deliquescent, Efflorescence, Hygroscopic substances: Caustic Soda, Iron(III) chloride, conc. sulphuric acid, sodium carbonate crystals, Quicklime, Epsom salt. (ii) Write the chemical formula of the salts: 1. Plaster of Paris 2. Gypsum [5] 3
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