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ST. STEPHENS SCHOOL DUMDUM PRE-BOARD EXAMINATION 2021 CHEMISTRY CLASS 10 ( Full Marks : 80 Time : 15 Mins Reading 2 Hours Writing 30 Mins Scanning & Making PDF ) You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of this paper is the time allowed for writing the answers. Section I is compulsory. Attempt any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) Attempt all questions from this Section Question 1 (a)Choose the most appropriate answer: [10] i) Among the period 2 elements, the element which has high electron affinity is a) Lithium b) Carbon c) Neon d) Fluorine ii) Compound X consists of only molecules. X will have a) Crystalline hard structure b) A low m.p & low b.p c) An ionic bond d) A strong force of attraction between its molecules iii) The formation of ethane from ethyne is an example of a) Addition reaction b) Substitution reaction c) Dehydration reaction d) Dehydrohalogenation reaction iv) Which of this will act as a non-electrolyte Protect by PDF Anti-Copy for Android (Update to Pro to remove watermark) a) Acetic acid b) Aqueous solution of sodium hydroxide c) Liquid carbon tetrachloride d) Aqueous solution of ammonia v) A substance which is used to increase conductivity of alumina a) Fluorspar b) Cryolite c) Aluminum d) sodium hydroxide vi) An example of an acid salt is a) Sodium acetate b) Sodium nitrate c) Di sodium hydrogen phosphate d) Sodium potassium carbonate vii) The hydroxide which is soluble in excess of NaOH is a) Zinc hydroxide b) Ferric hydroxide c) Ferrous hydroxide d) Magnesium hydroxide viii) The substance used for drying laboratory prepared hydrogen chloride gas a) Calcium oxide b) Phosphorus pentoxide c) Dilute sulphuric acid d) Concentrated sulphuric acid ix) Ammonia undergoes catalytic oxidation to produce a) Nitrogen b) Nitric oxide c) Nitrogen dioxide d) Nitric acid x) The final substituted product formed by the reaction of ethane & chlorine a) Chloro ethane b) Trichloro ethane c) Hexachloro ethane d) Ethyl chloride (b) State your observations for the following: [5] i) Ethene gas is passed through bromine solution. ii) Sulphur is reacted with conc. Sulphuric acid. iii) Dilute nitric acid is added to copper. iv) Electricity is passed through molten lead bromide. v) Dilute hydrochloric acid is added to the aqueous solution of lead nitrate. (c) Solve the following: [5] i) A gas cylinder filled with hydrogen holds 50g of the gas. The same cylinder holds 200g of gas A. Considering the same conditions of temperature & pressure calculate the relative molecular mass of gas A. ii) Empirical formula of a compound is XY2. If its empirical formula weight is equal to its vapour density, calculate the molecular formula of the compound. iii) State the empirical formula of a compound whose molecular formula is Na2S2H10O8. (d) Complete the following: [5] _____ & _____ participate in ionic bond formation. In covalent compounds if the combining elements have large difference in _______ then the bond formed is ______ bond. Hydronium ion is formed by ______ bond. (e) Write the IUPAC names of the following compounds: [5] (f) Give chemical equations for the following: i) C H +I ii) PbO+NH iii) NaHSO +H SO (dil.) iv) S+HNO (conc.) v) CHCl +I [5] (g) Rewrite each statements including appropriate conditions in your answer: [5] i) Water on electrolysis produces hydrogen & oxygen. ii) Ammonia turns red litmus blue. iii) Sulphuric acid is least volatile acid. iv) Magnesium reacts with nitrogen to form magnesium nitride. v) Hydrogen chloride gas is soluble in water. SECTION II (40 Marks) Attempt any four questions from this Section Question 2 [10] a) Atomic number of an element Z is 16. Answer the following: i) State the period & group to which Z belongs. ii) Is Z a metal or a non-metal? iii) State the formula of the compound between Z & hydrogen. b) First ionisation enthalpy of two elements X & Y are 500 kJ mol1- and 375 kJ mol1- respectively. Comment about their relative position in a group as well as in a period. c) State your observations for the following: i) Electrolysis of copper sulphate solution is done using platinum electrode. ii) Electrolysis of copper sulphate solution is done using copper electrode. Question 3 a) Show the formation of the following by electron dot structure: i) MgCl2 ii) CCl4 iii) H3O+ b) Explain the following: i) Methane is insoluble in water but soluble in acetone. [10] ii) Electrovalent compounds have high m.p & b.p. Question 4 [10] a) On heating 10g of CuSO4.xH2O crystals 6.4g anhydrous suplhate was left. Write the formula of the crystalline sulphate. [Cu=63.5, S=32, O=16, H=1] b) A salt has the following % composition: Zn=22.65%, S=11.15%, O=61.32% and H=4.88%. It s relative molecular mass is 287. Calculate its molecular formula assuming that all the hydrogen in the compound is present in combination with oxygen as water of crystallization. [Zn=65, S=32,O=16, H=1] c) Answer the following with respect to aluminium extraction: i) Give the chemical equations for the purification of bauxite by Baeyer s process. ii) Give the cathode & anode reaction for the electrolytic reduction of alumina. Question 5 [10] a) Solution P, Q, R has the pH 13, 6, 2 respectively. Which solution: i) will liberate ammonia from ammonium sulphate on heating? ii) is a strong acid? iii) contains molecules as well as ions? b) Classify the following salts as acid, basic & normal salt: KHCO3, CH3COONa, Cu(OH)Cl, NaHSO3 c) Give chemical equations for the following: i) Ammonium hydroxide solution is added to copper sulphate solution first in few drops & then in excess. ii) Potassium hydroxide solution is added to aluminium hydroxide. Question 6 [10] a) Answer the following with respect to the industrial preparation of nitric acid & laboratory preparation hydrochloric acid : i) Give the chemical equation of the reaction taking place at the catalytic chamber for the preparation of nitric acid by Ostwald s process. ii) Draw the funnel arrangement for the preparation of hydrochloric acid. b) Answer the following with respect to electroplating : i) State the name of the cathode, anode & electrolyte for electroplating an article by nickel. ii) Write the dissociation reaction & electrode reactions for the above mentioned process. c) Distinguish between the following by one chemical test : i) Sodium chloride & Sodium nitrate ii) Potassium sulphate & Potassium sulphite d) Give chemical equation to prove the following properties : i) Non-volatile nature of sulphuric acid ii) Burning of ammonia. Question 7 a) Answer the following with respect to isomerism : i) Draw all the possible isomers of butene. ii) State their IUPAC name. iii) Classify them as chain & position isomers. b) complete the following equation : i) C H +O ii) C H +2Cl iii) C H Cl +Cl [10]
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