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ICSE Class X Board Exam 2007 : Chemistry

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PART TEST-II_X_ICSE (ISO Certified Institute 9001 : 2008) 180 AJC Bose Road Kolkata 700014 033-40000460 / 9831818544 ------------------------------------------------------------------------------------------------------------------------------------------------------ CHEMISTRY SCIENCE Paper 2 (75 Minutes) [Total Mark : 50] --------------------------------------------------------------------------------------------------------Answers to this Paper must be written on the paper provided separately. Attempt all questions from Section I and any three questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. --------------------------------------------------------------------------------------------------------SECTION I [20 Marks] Answer all questions from this Section Question 1: a) Choose the correct answer from the options given below: [1 5=5] i) If empirical formula of an organic compound is CH2O then its molecular formula can be a) C2H2O2 b) C2H4O c) C3H6O d) C6H12O6 ii) Which salt cannot be directly used as an electrolyte? iii) iv) a) AgNO3 b) Na [Ag (CN)2] c) Both of them d) None of these The process used to convert impure alumina to pure alumina is: a) Electrolytic refining b) Purification c) Baeyer s process d) Roasting followed by calcination Electrolysis of fused lead bromide is carried out in a) a glass container b) an aluminium container c) a clay crucible d) a silica crucible www.transitioncs.com Copyright reserved v) b) c) Calcination process is generally used for a) Sulphite ores b) Sulphide ores c) Chloride ores d) Carbonate ores Fill in the blanks: [1 5=5] i) For the complete combustion of 1L propane, the required volume of oxygen at STP is ____________. ii) Volume of 4g oxygen is _____________ at STP. iii) Lower the position of ions in the electrochemical series, ____________ is the preference to get discharged at the respective electrode. iv) During electrolysis of acidulated water, volume of liberated hydrogen gas is ___________ the volume of liberated oxygen gas. v) The substance which is introduced during the smelting of ores to remove impurities is called ___________. Match the Column A with Column B. [1 5=5] Column A i) ii) iii) iv) v) d) Weak electrolyte Atoms in 18gm of water Froth flotation method Electroplating with silver Number of molecules in 88 gms of CO2 Column B a) b) c) d) e) Give one word or phrase for the following: i) ii) iii) iv) v) 18.066 1023 Sodium argentocyanide 12.044 1023 Acetic acid Sulphide Ores [1 5=5] Impurities which remain behind at the bottom of the cell. The law which stares that the gases react in definite volumes. The law which states that Equal volumes of all gases, under the similar conditions of temperature and pressure, contain equal number of molecules . Process by which impurities from metals are removed electrolytically. Zinc Oxide can be reduce to zinc by using. www.transitioncs.com Copyright reserved SECTION II [30 Marks] Answer any Threequestions from this Section Question 2: a) b) c) What volume of air (containing 20% O2by volume) will be required to burn completely 10 cm3 each of methane and acetylene? The compound A has the following percentage composition by mass: carbon 26.7%, oxygen 71.1%, hydrogen 2.2%. Determine the empirical formula of A. (Work to one decimal place) (H = 1; C= 12; O =16). If the relative molecular mass of A is 90, what is the molecular formula of A? i) State Avogadro s Law. ii) A cylinder contains 68 g of ammonia gas at s.t.p. 1) 2) 3) [3] [3] What is the volume occupied by this gas? How many moles of ammonia are present in the cylinder? How many molecules of ammonia are present in the cylinder? [4] Question 3: a) b) c) A metal article is to be electroplated with silver. The electrolyte selected is sodium argentocyanide. i) What kind of salt is sodium argentocyanide? ii) Why is it preferred to silver nitrate as an electrolyte? iii) State one condition to ensure that the deposit is smooth, firm and long lasting. iv) Write the reaction taking place at the cathode. v) Write the reaction taking place at the anode. [4] State the reaction occurring at the anode during electrolysis of: i) Copper sulphate solution using a copper anode. ii) Copper sulphate solution using a platinum anode. [2] With respect to the electrolysis of lead bromide, answer the following questions: i) Why is the lead bromide maintained in a molten state? ii) Why is the electrolytic cell made of silica? iii) Name the ions present in the electrolyte. iv) State what you observe at the (a) cathode (b) anode. v) Summarize the electrode reactions. [4] Question 4: a) i) ii) 1) What is an ore? 2) Name the two ores from which aluminium is extracted by electrolysis. Name an alloy of : 1) 2) b) c) Aluminium, used in aircraft construction. Copper, in electrical appliances or household vessels. [4] Explain why: i) In the electrolysis of alumina using the Hall Heroult s Process, the electrolyte is covered with powdered coke. ii) Iron sheets are coated with zinc during galvanization. [3] Answer the following questions w.r.t. Hall Heroult s process: i) Give the composition of electrolyte taken. ii) Why is powdered coke sprinkled over the surface of electrolytic mixture? iii) Give the reaction occurring at anode. iv) Why electrolytic reduction is preferred for aluminium? [3] Question 5: a) If a crop of wheat removes 20 kg of nitrogen per hectare of soil. Calculate the mass of Ca (NO3)2 required to replace nitrogen in 20 hectare field. (N = 14, O = 16, Ca = 40. Answer to the nearest kg) b) [2] What weight of sulphuric acid will be required to dissolved 3 g of magnesium carbonate? MgCO3 + H2SO4 MgSO4 + H2O + CO2 [Mg = 24, C = 12, O = 16] c) [2] Concentrated nitric acid oxidises phosphorus to phosphoric acid according to the following equation: P + 5HNO3 H3PO4 + 5NO2 + H2O www.transitioncs.com Copyright reserved i) What mass of phosphoric acid can be prepared from 6.2 g of phosphorus? ii) What mass of nitric acid will be consumed at the same time? iii) What would be the volume of steam produced at the same time if measured at 760 mm Hg pressure and 273 C? [H = 1; N = 14; O = 16; P = 31] d) e) [3] A 3.0 g sample of Na2CO3. 10 H2O is heated to a constant mass. How much anhydrous salt remains? [1 ] What percentage of water is found in Na2S.9H2O? [1 ]

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