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VIBGYOR HIGH Third Preliminary Examination AY 2020-21 CHEMISTRY Grade: X Max. Marks: 80 Date: 24/03/2021 Time allowed: 2 Hours _________________________________________________________ INSTRUCTIONS: 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 for writing the answers. Attempt all questions from Section I and any four questions from Section II. The intended marks for the questions or parts of questions are given alongside in brackets [ ] ___________________________________________________________________ SECTION-I (40 Marks) Attempt all questions from this Section Question 1 a Choose the correct answer from the options given below: (i) An element in period-3 whose electron affinity is zero: A He B Ne C D Ar Xe (ii) Which amongst the following is a characteristic of an electrovalent compound? A It is easily vaporised. B It has high boiling point. C It is a weak electrolyte. D It often exists as a liquid. 1 [5] [1] [1] (iii) An element X in period 2 of the periodic table is to the left of the element Y [1] in the same period. Y will have: A Larger atomic size than X B Lower ionisation potential than X C Lower electronegativity than X D None of the above (iv) The metallic electrode which does not take part in an electrolytic reaction: [1] A Copper B Silver C Platinum D Nickel (v) Ammonia gets oxidized in the absence of catalyst to form: A N2 and H2O B NO2 and H2O C NO and H2O D Cu b Write a balanced chemical equation for each of the following: [5] (i) Slaked lime is heated with ammonium sulphate. [1] (ii) Complete oxidation of methane. [1] (iii) Formation of 1, 2-dibromoethene from acetylene. [1] (iv) Decomposition of nitric acid at high temperature. [1] (v) Dissociation of aqueous solution of ammonia. [1] c State one relevant observation for each of the following reactions: [5] (i) Action of dilute hydrochloric acid on calcium hydrogen carbonate. [1] (ii) Ammonium sulphate is heated with sodium hydroxide solution and the gas [1] evolved is bubbled through copper sulphate solution. 2 [1] (iii) Moist blue litmus paper is introduced into the jar containing chlorine gas. [1] (iv) [1] (v) Sodium hydroxide is added drop wise till in excess to a solution of calcium nitrate. Action of ammonium hydroxide on iron (II) sulphate solution. d Give one word for the following statements: [5] (i) The particles that exist independently in solution. [1] (ii) Electrolytic cell used in the electrolysis of fused lead bromide. [1] (iii) The pH of pure water. [1] (iv) The element which has the lowest ionisation potential. [1] (v) The substance sprinkled over molten electrolytic mixture during the extraction of aluminium. [1] e Solve the following: [5] (i) 500 ml. of gas X at s.t.p. weighs 0.50 g. Calculate the vapour density and [2] [1] molecular weight of the gas. [1 lit. of H2 at s.t.p. weighs 0.09 g]. (ii) A compound of carbon, hydrogen and oxygen is found to contain 40% of [3] carbon, 6.7% of hydrogen and 53.3% of oxygen. Calculate its empirical formula and molecular formula. Vapour density of the compound is 30. [ C=12, H=1, O=16] f Fill in the blanks: [5] (i) In a covalent compound, the bond formed is due to the _________ of [1] electrons. (ii) Electroplating is done to protect the metal from_______. [1] (iii) Water cannot dissolve __________covalent compounds. [1] (iv) Nitre reacts with __________to produce vapours of nitric acid. [1] (v) Carbon dioxide and sulphur dioxide cannot be distinguished by using [1] __________. 3 g [5] 1. Draw the structural formula for each of the following: [2] (i) 1-butanoic acid [1] (ii) 2,2-dimethyl propane [1] 2. Write the IUPAC name for the following compounds: [3] (i) CH3-CH2-Cl [1] (ii) CH3-CH2-CH2-OH [1] (iii) CH3-CH2-CH=CH-CH3 [1] h Give appropriate reason for the following: [5] (i) Atomic radius of sodium is more than the atomic radius of chlorine. [1] (ii) Burning candle in an empty gas jar is extinguished when dry HCl gas is [1] poured into it. (iii) Ethane does not exhibit isomerism but butane does. [1] (iv) Potassium is considered as the most electropositive metal in the activity series [1] of metal. (v) Covalent compounds have low melting point and boiling point. [1] SECTION II (40 marks) Attempt any four questions from this Section Question 2 a Write the balanced chemical equation to show the formation of sulphur [2] dioxide from: (i) Dilute sulphuric acid [1] (ii) Concentrated sulphuric acid [1] 4 b Answer the following questions: [5] (i) What are non-polar covalent compounds? Give one example. [2] (ii) Which property of sulphuric acid allows it to react with sodium chloride? [1] (iii) State the technique used for separating ammonia from the uncombined [2] reactant mixture during Haber s process. Which physical property of ammonia is made useful in the technique? c Differentiate between the following pairs based on the information given [3] in the brackets: (i) Conductor and electrolyte(conducting particles) [1] (ii) Baeyer s process and Hall Heroult s process(method used) [1] (iii) Chain isomerism and position isomerism(difference in manner of linking of [1] atoms) Question 3 a Write the balanced chemical equation for the following reactions: [2] (i) Dissociation of aqueous formic acid. [1] (ii) Dissociation of aqueous sodium hydroxide. [1] b Name the following: [2] (i) A non-metal which reacts with concentrated nitric acid to form its own acid as [1] one of the products. (ii) The tendency of an atom to attract electrons to itself when combined in a [1] compound. c Group 1 2 13 14 15 16 17 18 Oxygen A Neon G B No. Lithium Carbon X Y C Z D 5 [6] In the Periodic Table given above, Lithium, Carbon, Oxygen and Neon are placed in their correct positions. The positions of eight other elements are represented by letters. These letters are not symbols for the elements concerned. (i) What will be the valency of X? [1] (ii) What type of bonds A can form with X? [1] (iii) How many electrons will be there in the valence shell of element A? [1] (iv) Which element is having the highest ionisation energy in this table? [1] (v) Amongst Li, X, Y and Z, which atom has the largest atomic size? [1] (vi) Which one is the most reactive non-metal? [1] a Answer the following questions: [3] (i) What is the purpose of pH scale? [1] (ii) Explain the term selective discharge of ions . [1] (iii) Give an example of a cyclic chain organic compound. [1] b Give reasons for the following: [3] (i) Electrolysis of water is not carried out on water acidified with dilute nitric acid. [1] (ii) HCl gas fumes in moist air. [1] (iii) A solution of silver nitrate is a good electrolyte, but it is not used for [1] Question 4 electroplating an article with silver. 6 c Match the description in Column 1 with the appropriate [4] substance/colour in Column 2. Write down the number of the description with the letter of the substance/colour. Sr. Column 1 Column 2 No. (i) A gas whose solution in water is alkaline. a) Hydrogen (ii) A gas which extinguishes a burning b) Ammonia splinter, but burns with a pale blue flame. (iii) Colour of the precipitate formed when zinc c) Carbon dioxide sulphate reacts with sodium hydroxide. (iv) A gas formed by burning of ethane. d) Blue e) White. Question 5 a With respect to the extraction of aluminium, answer the following [3] questions: (i) Give the chemical name and formula of the common ore of aluminium. [2] (iii) Why fused alumina cannot be reduced by using reducing agents? [1] A compound contains 87.5% by mass of nitrogen and 12.5% by mass of [3] b hydrogen. Determine the empirical formula of the compound. ( H=1, N=14 ) c Copy and complete the following paragraph using the options given: (Ammonia, Ammonium, Carbonate, Carbon dioxide, Hydrogen, Hydronium, Hydroxide, Precipitate, Salt, Water) A solution P turns methyl orange pink, so it must contain________ ions, another solution Q turns phenolphthalein pink and therefore it must contain ______ions. When solutions P and Q are mixed together, the products will be water and _______only. If a piece of zinc is put into the solution P , _____ gas would be evolved. 7 [4] Question 6 a Complete the following table relating to the laboratory preparation of [4] ammonia from ammonium salt: (i) (ii) (iii) (iv) State one precaution The reactant which Method How will to be taken during is used in a higher of you the preparation. identify ratio by weight. collection of the gas. the gas? ____________ b _____________ ________ _________ Distinguish between the following pairs of compounds using a reagent [3] as a chemical test: (i) Sodium sulphate crystals and ammonium sulphate crystals. [1] (ii) Sodium sulphite and sodium sulphate crystals. [1] (iii) Hydrochloric acid and calcium hydroxide solution. [1] c State which of the following are oxidised or reduced: [3] (i) O2- (ii) Fe3+ Fe2+ [1] (iii) Cl [1] [1] O Cl1- 8 Question 7 a An aqueous solution of nickel(II) sulphate is electrolyzed using nickel electrodes: State: [3] [1] a (i) The observation at the cathode. (ii) The cation that remains as spectator ion in the solution. b [1] ((iii) The nature of anode. [1] Answer the following: [4] (i) Name the kind of particles present in distilled water. [1] (ii) What is the special feature of the apparatus used for the preparation of nitric [1] acid in the laboratory? (iii) Which property of concentrated sulphuric acid is in action when sugar turns [1] black in its presence? (iv) Which reagent is used to test sulphide radical? [1] c Study the given diagram and answer the following questions: [3] (i) What will happen if a delivery tube is used instead of the above arrangement [1] during the preparation of acid? (ii) Name the arrangement shown. (iii) Name the type of particles present in the acidic solution. ***** 9 [1] [1]
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