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Class: X LOYOLA SCHOOL, BHUBANESWAR Pre-Board Examination, January - 2025 Subject: Chemistry F.M. = 80 Times: 2 Hrs. You will not be allowed to write during 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 Ais compulsory. Attempt any four questions from Section B. The intended marks for questions or part of questions are given in brackets [ ]. SECTION A [40 Marks] (Attempt all questions from this Section) Question 1 Choose the correct answers to the questions from the given options: (Do not copy the question,write the correct answers only). [15] (i) The ion which is discharged at the cathode during the electrolysis of copper sulphate solutions using copper electrodes as anode and cathode : (a) Cu2+ (b) OH(c) SO42(d) H+ (ii) A student took phenolphthalein in two different test tube marked as (I), (II).He added two compound A and B in test tube (I) and (II) respectively and observed,compound A turned into pink whereas compound B remain colourless. Conclusion drawn from the observation: (a) B is base but A is acid (b) B is acid but A is base (c) A is neutral but B is acid (d) B is neutral but A is acid (iii) The ratio between the number of molecules in 2 g of hydrogen and 32 g of oxygen is : (a) 1: 2 (b) 1 : 0.01 (c) 1 : 1 (d) 0.01 : 1 (iv) During the electrolysis of molten lead bromide which of the following takes place : (a) Bromine gas evolved at anode (b) Bromine gas evolved at cathode (c) Lead metal deposited at anode (d)Hydrogen gas evolved at cathode (v) Assertion (A) :Concentrated sulphuric acid is used for the preparation of hydrogenchloride gas or nitric acid. Reason (R) :Concentrated sulphuric acid is a good oxidising agent. (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is not the correct explanation of A. (c) A is true but R is false. (d) A is false but R is true. (vi) Product having fruity smell formed by the reaction between acid and an alcohol in presence of a catalyst is : (a) Ester (b) Carboxylic acid (c) Aldehyde (d) Ketone (vii) If M represents an atom of an alkaline earth metal,the correct formula of a compoundof this atom with sulphur is : (a) M2S (b) MS2 (c) MS3 (d) MS (viii) An element with the atomic number 19 will most likely combined chemically withthe element whose atomic number is : (a) 17 (b) 11 (c) 18 (d) 20 (ix) Which of the following hydroxides will not dissolve in excess of NH4OH, having dirty green colour? (a) Zn(OH)2 (b) Cu(OH)2 (c) Pb(OH)2 (d) Fe(OH)2 (x) Compound XY exist in solid crystalline form. The bond between X and Y is: (a) Ionic bond (b) Covalent bond (c) Coordinate bond (d) All of these (xi) Assertion (A) :Sodium and chlorine form ionic bond. Reason (R) :Sodium has a low ionization energy, while chlorine has a high electron affinity. (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is not the correct explanation of A. (c) A is true but R is false. (d) A is false but R is true. (xii) The number of moles present in 68 g of NH3 : (a) Two (b) Four (c) Five Page 1 of 4 (d) Ten (xiii) A chloride which does not show any change even in access of ammonium hydroxide is : (a) Calcium chloride (b) Ferrous chloride (c) Ferric chloride (d) Copper chloride (xiv) H3PO3 is an example of : (a) Monobasic acid (b) Dibasic acid (c) Tribasic acid (d) Diacidic (xv) The particles present in strong electrolytes are : (a) Only molecules (b) Mainly ions (c) Ions and molecules (d) Only atoms Question 2 [5] (i) Mr. Bhanu perform an experiment of electrolysis of copper (II) sulphate solution by adding dilute H2SO4 in trace amount and by using carbon as both cathode and anode and observed that blue colour of aqueous copper(II) sulphate solution remain unchanged. Based on his observation answer the following questions: (a) 1. Why the blue colour of electrolyte does not change? 2. What Mr. Bhanu observed at cathode? 3. What is the role of trace amount of dil. H2SO4 in acidified aq. copper sulphate solution? (b) Write the reactions involved at: 1. Cathode 2. Anode [5] (ii) Match the following Column A with Column B : ColumnAColumn B (a) Iron pyrites 1. FeCO3 (b) Cryolite 2. FeS2 (c) Calamine 3. Al2O3 (d) Siderite 4. Na3AlF6 (e) Corundam 5. ZnCO3 (iii) Complete the following by choosing the correct answers from the bracket : [5] a) The element at the bottom of a group would be expected to show metallic character than the element at the top (less, more). b) Reaction of acid with sodium carbonate releases .. gas. (CO2/ Cl2/ NO2) c) Conversion of ethanol to ethene is an example of (dehydration/ dehydrogenation)reaction. d) The general formula for alcohol is ( CnH2n+2 -OH / CnH2n+1 OH) e) Sulphuric acid is manufactured by .. process.(Contact/ Ostwald) (iv) Identify the following : [5] a) A drying agent which should not be used to dry hydrogen chloride gas. b) The compound formed by nitric acid which dissolves noble metals. c) The gas evolved at the anode during the electrolysis of acidified water. d) The compound that sticks to the glass apparatus during the laboratory preparationof hydrogen chloride. e) The tendency of an atom to attract the shared pair of electrons towards itself. (v) (a) Draw the structural diagram for the following compounds : 1. 2,3-dimethyl Butane2.1,1,2,2 tetrachloro ethane (b) Write down the IUPAC names of the following. 3. 2-Butanone [5] SECTION B (40 Marks) (Attempt any fourquestions) Question 3 (i) The element X has the electronic configuration 2,8,8,2. Without identifying X : (a) Predict the sign and charge of a simple ion of X . (b) Write if X will be an oxidising agent or a reducing agent and why? (ii) The metals of group 2 from top to bottom are Be, Mg, Ca, Sr and Ba. (a) Which of these elements will form ions most readily and why ? (b) State the common feature in the electronic configuration of all these elements. Page 2 of 4 [2] [2] (iii) The figure given below illustrates the apparatus used in the laboratory preparation of nitric acid. Observe the figure carefully and answer the given questions: [3] (a) Name A (a liquid), B (a solid) and C (a liquid). (b) Write an equation to show how C undergoes decomposition. (c) Write an equation for the reaction in which copper is oxidised by concentrated nitric acid solution. (iv) With respect to the extraction of aluminium answer the following: (a) Why powdered coke is sprinkled over the surface of electrolytic mixture? (b) Caustic alkali is added to bauxite ore during purification of bauxite. Give reason. (c) Why calcium fluoride is added to the electrolyte mixture of cryolite and alumina? Question 4 (i) The following questions relate the laboratory preparation of ammonia. (a) Why phosphorous pentoxide is not used as drying agent? (b) Ammonia gas is collected by downward displacement method. Give reason. (ii) Oxygen oxidises ethyne to carbon dioxide and water as shown by the equation: 2C2H2 + 5O2 4CO2 + 2H2O What volume of ethyne gas at STP is required to produce 8.4 dm3 of carbon dioxideat STP. [3] [2] [2] (iii) Element X is a metal with a valency 2. Element Y is a non-metal with a covalency 3. [3] (a) Write the chemical equation to show how X and Y form ions? (b) If Y ia a diatomic gas, write the chemical equation for the direct combination of X and Y to form a compound. (c)If the compound between X and Y is melted and an electric current passed through the molten compound, the element X will be obtained at the and Y at the . of the electrolytic cell. (iv) Write the balanced chemical equation for each of the following: (a) Burning of ethane in plentiful supply of air. (b) Action of water on calcium carbide. (c) Heating of ethanol at 170oC in the presence of conc. sulphuric acid. [3] Question 5 (i) Explain the following: [2] (a) Why are graphite anodes replaced from time to time during electrolytic reduction of aluminium? (b) Why ethene is more reactive than ethane? (ii) Draw the electron dot structure of: (a) Hydronium ion (b) Ammonium ion [2] (iii) Give a balanced chemical for the following reaction: (a) When butane is burnt in oxygen. (b) Ethene combines with hydrogen chloride. (c) Ethyl chloride reacts with alcoholic hot and conc. KOH. [3] (iv) A student was given a blue colour salt X for analysis. On strong heating it produces a white coloured residue and water vapour. The solution of salt X tested withexcess of ammonium hydroxide: (a) Identify the compound X . [3] (b) Write the observation when excess of ammonium hydroxide is added to thesalt solution. (c) What happens if the same salt solution is mixed with excess of NaOHsolution? Question 6 (i) Arrange the following according to the instructions given in brackets: (a) K, Pb, Ca, Zn (increasing order of the ionization energy) (b) Li, K, Na (decreasing order of electron affinity) Page 3 of 4 [2] (ii) Give reason for each of the following: [2] (a) Ionic compounds are bad conductor of electricity in dry and solid state. (b) The reducing power of elements decreases from left to right along a period in the periodic table. (iii) A compound is found to possess C=40%, H=6.7% and O=53.3%. its molecular mass is 60. Find the molecular formula of the compound. [3] (iv) Choose the correct word which refers to the process of electrolysis from A to E, to match the description (a) to (c). [3] A: Oxidation, B: Cathode, C: Anode, D: An electrolyte, E: Reduction. (a) Conducts electricity in aqueous or in molten state. (b) Loss of electron takes place at anode. (c) Electrode connected to the positive terminal of the battery. Question 7 (i) Calculate the number of moles in following: [3] (a) 4 g of sodium hydroxide (b) 224 litre of CO2 gas at STP (C) 6.022 x 1025 molecules of water. (ii) PH is defined as the negative logarithm of hydronium ion concentration. If H3O+> OH-, solution is acidic; if H3O+< OH-, solution is basic and if H3O+ = OH-, solution is neutral. [3] (a) What is the nature of pure water? (b) A compound changes methyl orange to yellow. What is its nature? (c) What changes can you observe on phenolphthalein in a neutral medium? (iii) Given below in column A is an experiment performed by a student with salt M and D. (a) Identify the anionwith the correct options from the column B . [4] Column A Column B (Experiment) (Anion) 1. Salt M on treatment withconc. sulphuric acid produces a gas whichfumes in moist air and gives dense white fumeswith ammonia. 1. 32 2. Salt D on treatment with dil. Sulphuric acid produces a gas which turns lime water milky but has no effect on acidifiedpotassium 2. NO3dichromate solution. 3. SO424. (b) When a pungent smelling gas P comes in contact with a glass rod dipped in liquid Q forms dense white fumes at the surface of the rod. Identify P and Q . Question 8 (i) Identify the following: (a) A colourless solution which gives white fumes with HCl. (b)A gasevolved when hydrogen chloride is added to magnesium carbonate. (ii) Differentiate between the following pairs: (a) Ionization and Dissociation (b) Polar and non- polar covalent bond (iii) Name the following: (a) An alloy of aluminium used in aircraft construction (b) A metal which is always present in amalgam. (c) The constituents of Brass. (iv) Ram wants to keep a practical notebook based on his visit to the chemistry lab. What should he note for records in the following experiments? (a) Conc. nitric acid is added to sulphur powder. (b) Ammonia gas is passed over heated copper (II) oxide (c) Lead nitrate solution is treated with NaOH solution drop wise till it is in excess. ***************All the best *************** Page 4 of 4 [2] [2] [3] [3]
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