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ST. MICHAEL'S SCHOOL, SILIGURI (BOYS' WING) PRE BOARD EXAM 2023-2024 SUBJECT: CHEMISTRY CLASS 10 (SCIENCE PAPER II) Maximum Marks: 80 Time allowed: Two Hour Answers to this paper must be written on the paper provided separately. 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 f or writing the answers. Section A is compulsory. Attempt any FOUR questions from Section B. The intended marks for questions or parts of questions are given in brackets [ ] Section A (Attempt all questions from this section.) QUESTION 1 Choose the correct answers to the questions from the given option: [15] 1) The type of reaction taking place between alkane and halogens : a) Combustion b) Oxidation c) Hydrogenation d) Halogenation 2) Sodium hydroxide is added to the salt solution and shows different observations. Identify the correct set of observations from the given table: Salt Solution Colour of Precipitate Solubility in excess of NaOH W Fe(OH)3 Dirty Green Insoluble X Pb(OH)2 White Soluble Y Zn(OH)2 White Soluble a) Only W b) Both X and Y c) Both W and Y d) Both W and X Page 1 of 8 3) What impurity causes the yellow colour in concentrated nitric acid? a) Hydrogen b) Nitrogen c) Nitrogen dioxide d) Nitrogen mono oxide 4) Excess ammonia reacts with chlorine liberating the gas : a) Chlorine b) Nitrogen c) Hydrogen d) Hydrogen chloride 5) Which of the following combination is true for carrying out electroplating of an object? a) Direct and large current b) Alternating and small current c) Alternating and large current d) Direct and small current 6) Which of the following statements is not a correct statement about the trends when going from left to right across the Periodic Table? a) The elements becomes less metallic in nature b) The atoms lose their electrons more easily c) The number of valency electrons increases d) The oxides become more acidic 7) The molecular formula of an organic compound is H4C2O4 .Then its empirical formula is a) HCO2 b) H2C2O2 c) H2CO d) H2CO2 8) The bond formed between the atom of a group I metal and that of a group VI element is : a) Electrovalent b) Covalent c) Non polar covalent d) Coordinate covalent 9) A chloride which does not show any change even in excess of ammonium hydroxide is : a) Calcium chloride b) Ferrous chloride c) Ferric chloride d) Copper chloride Page 2 of 8 10) Which acid does not evolve H2 gas with metals? a) H2SO4 b) HNO3 c) HCl d) All of these 11) Which ion gets deposited first at cathode during the electrolysis of the solution containing Cu+2, H+, Fe+3 and Zn+2 ion? a) Copper ion b) Hydrogen gas c) Iron ion d) Zinc ion 12) The functional group present in vinegar is a) Ketonic group b) Aldehydic group c) Carboxyl group d) Hydroxyl group 13) Which one of the following will not produce an acid when made to react with water? a) Nitrogen dioxide b) Carbon dioxide c) Carbon monoxide d) Sulphur trioxide 14) If the empirical formula of a compound is CH and its vapour density is 13, then its molecular formula will be (At. Wt. C=12, H=1) a) CH b) C2H2 c) C4H4 d) C3H3 15) Dilute sulphuric acid produce a white precipitate when added to a solution of a) Copper nitrate b) Zinc nitrate c) Lead nitrate d) Sodium nitrate Page 3 of 8 QUESTION 2 1) The diagram shows an experimental setup for the electrolysis for lead bromide. Answer the following questions: [5] a) Why silica crucible is used in the above process? b) Why Platinum electrodes are not used in this process? c) What is observed at each of the electrodes? d) Why is the electrolyte heated externally? 2) Match the column A with column B: Column A Column B A Sulphur trioxide 1 Drying agent B Calcium oxide 2 Anhydride of sulphuric acid [5] C Iron 3 Burning sulphur smell D Calcium carbide and water 4 Catalyst E Sulphur dioxide 5 Ethyne 3) Complete the following by choosing the correct answers from the bracket: [5] a) The polar covalent compound in gaseous state that does not conduct electricity is ..(Carbon tetrachloride/Ammonia/ Methane) b) An alkali that completely dissociates into ions is ..(Ammonium hydroxide/Calcium hydroxide/Lithium hydroxide) c) The number of mole in 11 gm of nitrogen gas is .. (0.39, 0.49, 0.29) d) Converting ethanol to ethene requires the use of (conc. HCl, conc.HNO3, conc.H2SO4) e) When hot concentrated sulphuric acis is added to sulphur, it get oxidized to (SO3, H2S, SO2) 4) Identify the following : [5] a) The solution that turns brown when it comes in contact with ammonia. b) A metal which reacts with very dilute nitric acid. c) A metal nitrate which leaves no residue on heating. Page 4 of 8 5) d) The cation whose chloride salt when treated with ammonium hydroxide gives dirty green precipitate. e) The gas liberated when zinc is treated with hot conc. KOH. a)Draw the Structural formula for the following: [5] a) 2-propanol b) 2-methyl pentane b) Give the IUPAC name for each of the following : a) H-CHO b) C2H5OH c) H3C-CH = CH CH3 SECTION B ATTEMPT ANY FOUR QUESTIONS QUESTION 3 (i) A non volatile oily acidic liquid A poured on blue crystalline substance B which gives white amorphous powder C. [2] a) Give the relevant chemical equation. b) Name the process involved. (ii) Give balanced chemical equations for the preparation of the following organic compounds: [3] a) A saturated hydrocarbon from iodomethane. b) An unsaturated hydrocarbon from alcohol. c) Alcohol from alkyl halide. (iii) Compound A is bubbled through bromine dissolved in carbon tetra chloride and the product is CH2Br CH2Br. A 2 4 CH2Br CH2Br. [3] a) Draw the structural formula of A. b) What is your observation? c) Name the compound formed when steam reacts with A in the presence of phosphoric acid. (iv) Pungent smelling gas A when comes in contact with a glass rod dipped in liquid B, forms dense white fumes at the surface of the rod. Identify A and B and write relevant equation taking place. [2] QUESTION 4 (i) (a) Calculate the number of atoms in the 6.3 grams of nitric acid. (b) What do you observe when ammonia is passed over heated Copper oxide? [2] (ii) Draw the electron dot structure of : [2] a) Sodium chloride[Na =11, Cl = 17] b) Ammonium ion [ N= 7, H=1] Page 5 of 8 (iii) Answer the questions (a) to (c) on the basis of metallurgy of aluminium. [3] a) Explain the function of cryolite. b) Why fluorspar is added to alumina? c) Why graphite rods are replaced from time to time during the extraction of aluminium from its ore? (iv) (a)What is the property of concentrated sulphuric acid which allows it to be used in the preparation of hydrogen chloride and nitric acid? [3] (b) What property of hydrogen chloride is demonstrated when it is collected by downward delivery ? (c) What is observed when, neutral litmus solution is added to sodium hydrogen carbonate solution? QUESTION 5 (i) An inorganic compound contains 40% calcium, 12% carbon and 48% oxygen. If its molecular weight is 100g, calculate its molecular formula. ( Ca=40, C=12, H=1) [2] (ii) What do you observe? [3] a) Copper oxide treated with sulphuric acid. b) When barium chloride solution is added to dilute sulphuric acid. c) Dilute Hydrochloric acid is added to Lead nitrate solution and the mixture is heated. (iii) With reference to Haber s process for the preparation of ammonia, answer the following: [3] a) Write the balanced equation and the conditions required. b) In what ratio by volume, are the above gasses used? c) Mention one way to collect ammonia gas from unchanged gases. (iv) With respect to laboratory preparation of hydrogen chloride gas :[3] a) Write the equation for its preparation mentioning the condition required b) Name the drying agent used and justify your choice. c) State a safety precaution you would take during the preparation of hydrochloric acid. QUESTION 6 (i) Distinguish between the following pair of compounds: a) Sodium sulphate and sodium sulphite. b) Ammonium hydroxide and sodium hydroxide. c) Magnesium chloride and magnesium sulphate. [3] Page 6 of 8 (ii) Give balanced chemical equations for the following conversions A ,B and C: [3] Fe FeCl3 FeCO3 Fe(NO3)2 (iii) Write the electrode reactions when the following chemicals are electrolyzed? [2] Chemical Reaction at cathode Reaction at anode Molten lead bromide Aqueous CuSO4 solution with coper electrodes (iv) Arrange the following as per the instruction given in the brackets. [2] a) Na, Al, Cl, Mg, P(increasing order of ionisation potential). b) Zn2+, Na+, Cu2+ (order of preference of discharge at the cathode). QUESTION 7 (i) Choose the major metals to make the following alloys: [2] a) Stainless steel b) Brass (ii) Write the products and balance the equation. [2] a) PbO + NH3 b) MnO2 + conc. HCl (iii) Identify the acid which matches the following description (a) to (c) [3] a) The acid which is used in the preparation of a non-volatile acid. b) The acid which produces sugar charcoal from sugar. c) The acid which is prepared by catalytic oxidation of ammonia. (iv) The following table represents the elements and the atomic number. With reference to this, answer the following using only the alphabets given in the table. [3] Element Atomic number P 13 Q 7 R 10 a) Which element combines with hydrogen to form a basic gas? b) Which element has an electron affinity zero? c) Name the element, which forms an ionic compound with chlorine. Page 7 of 8 Question 8 (i) How much calcium oxide is formed when 82 g of calcium nitrate is heated? Also find the volume of nitrogen dioxide evolved: [2] 2Ca(NO3)2 2CaO + 4NO2 + O2 (Ca = 40, N = 14, O =16) (ii) Give balanced chemical equations for the following. [2] a) Copper carbonate is treated with sulphuric acid. b) Zinc hydroxide is heated in presence of sodium hydroxide. (iii) (a)Write the equation for the preparation of ethylene from ethyl alcohol. (b) Write the equation for the catalytic oxidation of sulphur dioxide to sulphur trioxide. (c) Name an amphoteric oxide reduced by heating with carbon. [3] (iv) Acidulated water is electrolysed in Hofmann s voltameter to liberate two gases. In this context answer the following questions. [3] (a) Name the gases evolved at each electrode. (b) What is the material used for electrodes? (c) What is the ratio of gases evolved by volume? Page 8 of 8
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