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CHEMISTRY SCIENCE PAPER 2 (2 hours) Answer 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 reading the question paper. The time given at the head of this paper is the time allowed for writing the answers. Attempt all the questions in Section I and any 4 from Section II. The intended marks for questions is given in the brackets [ ]. SECTION I (40 marks) Attempt all the questions from this section Question 1 (a) Choose the right answer from the options given below: (i) [5] Dilute sulfuric acid is added to the electrolyte aqueous copper sulfate because it: A. Enhances conductivity of the electrolyte. B. Prevents hydrolysis of the electrolyte. C. Both A & B. D. None of the above. (ii) Which of the following reactions will take place? [Hence, write a balanced equation for the chosen reaction.] A. Mg + CaSO4 B. Al + FeCl3 C. Pb + NaNO3 D. Ag + CuSO4 (iii) The volume of oxygen required and volume of nitric oxide formed when 100 ml of ammonia is catalytically oxidized is: A. 125 ml of O2 and NO each B. 125 ml of O2 and 100 ml NO C. 100 ml of O2 and NO each D. 125 ml of O2 and 100 ml of NO 1 Turn Over (iv) P is a salt whose solution is neutral. Q is a salt whose solution is acidic. The anion common to P and Q is: A. SO42B. CO32C. ClD. NO3(v) The IUPAC name of: is: A. 2-methyl hexan-4-al B. 2-ethyl 4-methylpentanal C. 2-ethylhexanal D. 4-methyl 2-ethylpentanal (b) State the property of the following substances which enables them to be used in the process mentioned in the brackets: (i) [5] Ammonia (as a refrigerant) (ii) Molybdenum (in Haber s process) (iii) Tin (in solder) (iv) Acetylene (in welding of metals) (v) Sodium argentocyanide (in electroplating of silver) (c) Give a suitable word/term for the following: (i) [5] Hydroxy derivatives of alkanes formed by replacement of hydrogen atoms of alkanes by corresponding number of hydrogen atoms. (ii) The formula of a compound which shows the simplest whole number ratio between the atoms of the elements in the compound. (iii) The process by which ammonium salts are prepared in the laboratory. (iv) The process by which acidulated water is electrolyzed. (v) A bond which involves one of the combining atoms contributing both of the shared electrons. (d) Write one relevant observation for each of the following cases: (i) [5] The odor of the gas evolved when ammonium nitrate is heated is smelt by a person. (ii) The graphite anode in Hall Heroult s process. (iii) Acetic acid when cooled to 15 C. 2 Turn Over (iv) Drops of hydrochloric acid are added to a test tube containing ground manganese dioxide and moist starch test tube is exposed to the test tube. (v) Ammonium hydroxide is added to calcium nitrate. (e) Give reason for the following: (i) [5] Nitric acid yields both nitrogen monoxide and nitrogen dioxide when the same metal reacts with it at different temperatures. (ii) For construction work, the alloy duralumin is used rather than pure aluminum. (iii) In electroplating of metals, a low direct current should be used for a longer time. (iv) A given organic compound can be assigned only one name on the basis of IUPAC system. (v) The reaction between lead oxide and dilute sulfuric acid almost does not take place. (f) Identify the gas evolved in the following cases: (i) [5] Electricity is passed through molten lead bromide. (ii) Ammonium nitrite undergoes thermal decomposition. (iii) Concentrated sulfuric acid is added to sulfur powder. (iv) Cold dilute nitric acid is added to zinc granules. (v) Coke is added to lead oxide. (g) Write a balanced chemical reaction for the following reactions: (i) Aluminum reacts with hot concentrated caustic soda. (ii) Excess ammonium hydroxide is added to a solution of copper hydroxide. (iii) Hydration of ethene in the presence of phosphoric acid. (iv) Complete combustion of ethane. (v) Reaction of quick lime with dilute hydrochloric acid. (h) The volumes of gases A, B, C and D are in the ratio 1 : 2 : 2 : 4 under the same condition of temperature and pressure. (i) Which sample of gas contains the maximum number of molecules? (ii) If the temperature and pressure of the gas A are kept constant, then what will happen to the volume of the gas A ? (iii) If this ratio of gas volumes refers to the reactants and products of a chemical reaction, which gas law is being observed? State the law. (iv) If the volume of A is actually 5.6 dm3 at S.T.P., calculate the number of molecules in the actual volume of gas B at S.T.P. (Take Avogadro s number: 6 x 1023) (v) State the mass of gas D if the gas is nitrous oxide. (N = 14, O = 16) [5] 3 Turn Over SECTION II (40 marks) Attempt any 4 of the questions from this section Question 2 (a) During the electrolysis of concentrated solution of sodium chloride: (i) State your observation at the anode. (ii) Write an equation for the reaction at the cathode. (iii) What difference would you observe, if the electrolyte is replaced with fused sodium chloride? [3] (b) Write the IUPAC name of the compounds given below. (i) [3] (iii) (ii) (c) A sample of hematite is found to contain about 60% of ore and 40% of silica, metallic chlorides. (i) Name the method you would employ to concentrate the ore. Give reason to justify your answer. (ii) Is roasting or calcination necessary for this ore? If so, write a balanced equation to represent the process. (iii) Mention the metallurgical term for the silica and chlorides present in the sample. (iv) How would you obtain the pure metal from the ore? Give a balanced equation to represent this process. (v) What changes would be there in your answers (i) to (iii) if the sample of ore is changed to iron pyrites? [4] Question 3 (a) Arrange the following chemicals as per the instructions specified in the brackets. (i) [4] SiO2, P2O5, Al2O3, MgO, SO2, Na2O. [increasing order of acidity] (ii) Na, Hg, Fe, Cu, Al, Zn. [decreasing order of affinity for oxygen] (iii) Cl, P, Al, S, Mg, Na [increasing order of electronegativity] 4 Turn Over (iv) 2.5 gram molecules of oxygen, 2.5 moles of lead, 18.06 1023 molecules of sulfuric acid, 2.5 liters of hydrogen sulfide gas at S.T.P. [increasing order of mass] [H= 1, O = 16, S = 32, Pb = 207, Avogadro s number = 6.02 1023] (b) In the given section of the modern periodic table, H does not represent hydrogen and I does not represent iodine. Some elements are in their own symbol and position while others are shown with a letter. Use the letters only given in the periodic table below to answer the following questions: Group 1 1st period G 2nd period Li 3rd period 4th period (i) 2 [6] 13 14 15 16 17 0 H E D O I Si U L Name the element with highest electronegativity. (ii) Identify the elements which have the highest and lowest ionization potential. (iii) What is the electron affinity of L? (iv) Which is the most reactive metal shown in the above table? (v) Mention one element which forms covalent bonds. (vi) Which one of the elements has the largest atomic radius? Question 4 (a) An element P has an atomic number 12 and Q has an atomic number of 17. (i) [4] State the kind of bonding existing between these two elements and draw the electron dot structure of the compound formed. (ii) Is the bonding polar or non-polar? Give reason. (iii) Name one compound which has all ionic, covalent and electrovalent bonding in its structure. (iv) Draw the electron dot structure of the cation present in the compound mentioned in (iii). (b) Determine the molecular formula of a compound containing potassium, iron, carbon and nitrogen only and having a relative molecular mass of 368. The percentage composition of the first three elements are 42.5%, 15.2% and 19.5% respectively. [K = 39, Fe = 56, C = 12, N = 14] (c) (i) [3] State two methods by which the yellowish brown tinge of the nitric acid can be removed. 5 Turn Over (ii) What is the molar ratio of the reactants in the laboratory preparation of nitric acid? Why? [3] Question 5 (a) State giving reasons which of the below substances in each case is odd or differs from others. (i) [4] Silver [I] chloride, mercury [I] chloride, lead sulfate, lead nitrate, lead chloride. (ii) Water, ammonia, hydrogen chloride, hydrogen fluoride, hydrogen. (iii) Carbon dioxide, sulfur oxide, oxygen, chlorine, nitrogen dioxide. (iv) C7H16, C6H10, C8H14, C5H8. (b) A teapot is to be electroplated with silver. The setup is shown below. Answer the following questions with reference to the diagram. (i) [4] Which electrode is the oxidizing electrode? Why? (ii) Identify solution X. Why is it better than any other solutions that can be used for the process? (iii) How does X dissociate? Represent it in the form of equation. (iv) Which is the cathode in the setup? Write an equation at the cathode. Also, state what you would observe in the other electrode. (c) A green crystalline solid G on strong heating turns reddish brown. The evolved gas is passed through acidified potassium permanganate solution which turns from pink into a clear colorless solution. (i) State the cation and anion present in G. (ii) What would you observe when drops of ammonium hydroxide solution is added to G first in small amounts and then in excess? [2] Question 6 (a) Bromine is dissolved in an inert solvent carbon tetrachloride. The solution when measured weighed 26.4 g. When some amounts of ethene is bubbled through the solution, 4.7 grams of ethylene dibromide is formed. (i) Calculate the percentage of bromine in the solution. 6 Turn Over (ii) The volume of ethene passed through the solution at S.T.P. (iii) State your observation of this reaction. [C = 12, H = 1, Cl = 35.5, Br = 80] [3] (b) Study the following chart and answer the following questions. (i) [4] Identify A, B and M. (ii) Write a balanced equation for conversion 1 and 2. (iii) Identify the process P. Give balanced equation stating any three conditions. (iv) How will the metal M react with ammonia? What will you observe during this reaction? (c) (v) What do you observe when crystals of sugar are placed in concentrated sulfuric acid? Give reason for your observation. (vi) Write a balanced molecular equation for the reaction in (c) (i). (vii) Besides n-Hexane, draw any two other isomers of hexane and mention its IUPAC name. [3] Question 7 (a) Certain substances from the list given below react together to give salts. Choose the correct substances from the list to prepare the following salts. Also, write the correct equations for these preparations. [5] Copper, Sulfur, dilute sulfuric acid, sodium carbonate, potassium hydroxide, Barium sulfate, Zinc, Iron, Ammonium hydroxide, Calcium chloride, dilute Nitric acid. (i) Zinc sulfide (ii) Potassium sulfate (iii) Barium nitrate (iv) Copper carbonate (v) Calcium carbonate 7 Turn Over (b) Give the structural formula of the following. (i) [2] An unsaturated hydrocarbon which undergoes catalytic hydrogenation to given ethane as the final product. (ii) A substance obtained by the reaction of an alcohol with an acid. (iii) A gas liberated by the action of cold water on calcium carbide (iv) An organic compound whose trivial name is acetone. (c) (i) Name an acid other than nitric acid which can be prepared from concentrated sulfuric acid. (ii) Write a balanced equation for the above preparation. (iii) Name the drying agent used in the above preparation. State why this reagent is preferred to any other drying agent. (iv) Give two reason why concentrate sulfuric acid is used in the preparation. [3] [This paper consists of 8 printed pages] 8 Turn Over
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