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ICSE Prelims 2017 : Chemistry Must Know Questions(Chatrabhuj Narsee Memorial School (CNM), Mumbai)

9 pages, 121 questions, 121 questions with responses, 241 total responses,

Sanchit Modi
Bhaktivedanta Swami Mission School (BSMS), Mumbai

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Shri Vile Parle Kelavani Mandal s C.N.M. School & N.D. Parekh Pre-Primary School MUST KNOW QUESTIONS (2016-17) CHEMISTRY I. PERIODIC PROPERTIES AND VARIATIONS OF PROPERTIES 1) Define -Ionization potential 2) Differentiate between electron affinity and electronegativity. 3) Give reason: A cation is smaller in size than its parental atom. 4) Complete the following table by filling the word INCREASE or DECREASE Periodic property Across a period from left to right Down the group from top to bottom 1. Atomic size 2. Ionization potential 3. Electro affinity 4. Electro negativity 5. Metallic character II. CHEMICAL BONDING 1) Explain why polar covalent compounds can conduct electricity in their aqueous state. 2) Draw electron dot structures of hydronium & ammonium ion. Label the lone pair of electrons. 3) Differentiate between sodium chloride and carbon tetra chloride on the basis of following points. (i) Type of bonding (ii) Dissociation in solution (iii) Conductivity 10-chemistry Page 1 4) Draw the structure of following compounds (i) Sodium chloride (ii) methane III. STUDY OF ACIDS,BASES AND SALTS 1) Differentiate between deliquescence and efflorescence. 2) Give reason: (i) Iron (III) chloride is stored in air tight bottles. (ii) Sulphurous acid forms two types of salts on reaction with an alkali. 3) Give balance chemical reaction showing preparation of following salt. Also state the method involved. (i) Sodium sulphate (ii) Zinc sulphide (iii) Copper sulphate (iv) Zinc chloride (v) Calcium carbonate IV. ANALYTICAL CHEMISTRY 1) Sodium hydroxide solution can be used to distinguish between Iron (II) sulphate and Iron (III) sulphate solution: because these solutions give different coloured precipitate with sodium hydroxide solution. Give the colour of the precipitate formed with each of the solution. 2) You are given three white powders-calcium carbonate, lead carbonate and zinc carbonate. Describe the test you would carry out in solution, to identify the metal ion in each of the above compounds. Indicate clearly how you would prepare the solutions for the tests. 3) Describe in each case, one chemical test that would enable you to distinguish between the following pairs of chemicals. Describe what happens with each chemical or state no visible reaction . (i) Sodium chloride solution and sodium nitrate solution (ii) Calcium nitrate solution and zinc nitrate solution (iii) Zinc sulphate solution and zinc nitrate solution. 4) Write the balanced equations for the following reactions: (i) Iron (II) chloride solution with sodium hydroxide solution (ii) Sulphur dioxide and sodium hydroxide solution. (formation of normal salt) 5) Identify the substances P,and Q in each case based on the information given below: 10-chemistry Page 2 (i) The deliquescent salt P, turns yellow on dissolving in water, and gives a reddish brown precipitate with sodium hydroxide solution. The white crystalline solid Q is soluble in water. It liberates a pungent smelling gas when heated with sodium hydroxide solution. (ii) V. MOLE CONCEPT AND STOICHIOMETRY 1) Determine the empirical formula of the compound whose composition by mass is 29.11 % Sodium, 30.38 % oxygen and 40.5 % Sulphur. (S= 32: Na = 23; O = 16). 2) 4.5 moles of calcium carbonate are reacted with dilute hydrochloric acid (i) Write the equation for the reaction (ii) What is the mass of 4.5 moles of calcium carbonate? (Relative molecular mass of Calcium carbonate is 100) (iii) What is the volume of carbon dioxide liberated at STP? (iv) How many moles of HCl are used in this reaction? (v) What mass of calcium chloride is formed? (Relative molecular mass of Calcium chloride is 111 ) 3) (i) A compound has the following percentage composition by mass: carbon 14.4%, Hydrogen 1.2% and chlorine 84.5%.Determine the empirical formula of this compound. Work correct up to 1 decimal place. (ii) The relative molecular mass of this compound is 168,so what is its molecular formula? (iii) By what type of reaction could this compound be obtained from ethyne? 4) What volume of oxygen would be required for the complete combustion of 200 litres of ethane according to the following equation? 2C2H6 + 7O2 4CO2 + 6H2O. 5) 280 ml of carbon monoxide is mixed with 250 ml of oxygen and ignited. The chemical equation for the reaction is as follows: 2CO + O2 2CO2. Calculate the volume of oxygen used and carbon dioxide formed in the above reaction. 10-chemistry Page 3 VI. ELECTROLYSIS Sr. Electrolytic cell 1 Molten Electrolyte Dissociation of electrolyte Material cathode of Material of anode Reaction and product at cathode Reaction and product at anode lead bromide 2 Acidified water 3 Aqueous Copper Copper copper sulphate 4 Electroplating on a nail with nickel 5 Electroplating of a spoon with silver 6 Electro refining with copper 1) 2) 3) 4) 5) List the main precautions to be taken during electroplating. For electroplating with silver, silver nitrate is not used as electrolyte. List the factors that influence the preferential discharge of ions at the electrodes. Define electrolysis The volume of hydrogen and oxygen formed at the cathode and anode are 2:1 by volume respectively. 6) During electroplating a small current should be used for a longer time. 10-chemistry Page 4 VII. METALLURGY 1) What is rusting? Give an equation that shows the rusting of iron. 2) Give the 3 equations that represent the purification of aluminium ore by Baeyer s process. 3) Give the name of the constituents of the electrolyte used in the Hall-Heroult s process. Write the equations occurring at both the electrodes. 4) Why is sodium hydroxide used in the concentration of bauxite? 5) Define alloy. 6) What are the constituents of Brass and Steel? 7) Differentiate between a metal and non-metal on the basis of the oxides they form. 8) Name two methods by which iron metal can be protected from rusting. 9) Name a non-metal that conducts electricity. 10) Why metals are called reducing agents? 11) What can you say about bonding seen in metallic chlorides? VIII. STUDY OF COMPOUNDS-HCl,AMMONIA,NITRIC ACID AND SULPHURIC ACID Manufacture of sulphuric acid: Compounds Name of process Reactants Temperature Pressure Catalyst Sulphuric acid Write the reactions of the above process: 1) Burning of pyrites to form SO2 ............. 2) Conversion of SO2 to SO3 ..................... 3) Conversion of SO3 to Oleum ................. 4) Conversion of Oleum to Sulphuric acid . Reactions of Sulphuric acid showing the properties of the acid as:I As a Typical dilute acid Action With 1) Metals Zinc and Iron (not Cu and Pb) ....... 2) Carbonates and bicarbonates .......... 10-chemistry Page 5 3) Sulphites and Bisulphites .. ........... 4) Sulphides (FeS) .. ........... 5) Alkalis/ basic oxides/ bases .. .............. II - As an Oxidizing reactions (showing oxidizing property of conc Sulphuric acid) 1) Carbon (oxidation of non-metals) .. .... 2) Sulphur (oxidation of non-metals) .. . .... 3) Cu or Zn (oxidation of metals) .. .. .... III - As a Dehydrating Property (conc Sulphuric acid) dehydration of 1) Sugar / glucose .. .. .... 2) Hydrated copper (II) sulphate (blue crystals) .. 3) Ethyl alcohol . .. .... IV. As a Least Volatile Acid (conc Sulphuric acid) - Reaction with 1) Sodium chloride .. .. .... 2) Potassium nitrate .. . .... Test of Sulphuric acid- or any sulphate (contains SO 4- - anion) 3) Reaction with BaCl2 .. . .... 4) Reaction with Lead nitrate .. .. .. Ammonia: The table below shows the manufacture of Ammonia, complete by filling appropriate data:Compound 1 Process Reactants Temperature Pressure Catalyst NH3 II) Write balanced equations for the following reactions, write any special conditions required. 10-chemistry Page 6 1) Ammonia is passed over hot oxides of copper, lead and iron (which property of ammonia is shown) 2) Catalytic oxidation of NH3 by platinum. In which process is it used? 3) Excess of chlorine reacts with NH3 4) Excess of NH3 reacts with Cl2 Nitric acid: Explain:1) In lab preparation of nitric acid the entire apparatus is made up of glass only. 2) Dil. Nitric acid does not give hydrogen gas with metals like other dil. acids. 3) Pure nitric acid is colourless yet in the labs the acid is little yellowish. 4) In the brown ring test for nitric acid / nitrates, ferrous sulphate used should be freshly prepared. Hydrogen chloride and Hydrochloric acid Write balanced equations for the given reactions:1) Sodium chloride is treated with conc. Sulphuric acid. (below and above 200 o C) 2) Hydrogen chloride gas is bubbled through lead nitrate solution. 3) Conc. Hydrochloric acid is oxidized by lead (IV) oxidePbO 2/ MnO2/ Trilead tetra oxide/KMnO4. 4) Hydrochloric acid is added to sodium thiosulphate (write observation also) Explain why? 1) The temperature of the apparatus should not be above 200oC while preparing hydrogen chloride gas in the lab. 2) Hydrogen chloride cannot be dried using quick lime or phosphorus pentachloride. 3) HCl being a covalent compound behaves like an electrovalent compound when dissolved in water. 4) Dry HCl does not turn blue litmus red. IX. ORGANIC COMPOUNDS Write balanced equations for the preparation of the following: 1) methane from sodium ethanoate. 2) Ethene from ethyl bromide. 3) Ethyne from calcium carbide 4) Ethanoic acid from ethanol 5) Ethanol from ethane 6) Ethyl acetate from ethanoic acid 10-chemistry Page 7 Draw the structural formula of : 1) Acetone 2) iso butane 3) ethanoic acid 4) 1,1-dichloropropane 5) Methoxy methane Name the following structures: X. PRACTICAL WORK Q. 1.Identify the anion present on the basis of these reactions. 1) Silver nitrate solution is added to a solution of A to give a white precipitate insoluble in nitric acid. 2) Dilute HCl. Is added to a solution of B to give a gas which turns lead acetate silver black. 3) Freshly prepared solution of ferrous sulphate is added to a solution of C and conc. Sulphuric acid is added from the sides. A brown ring is obtained. Q 2. You are provided with only two reagents dil. HCl and BaCl2 solution. Two white salts sodium carbonate and sodium sulphate are given. How can you identify them? 10-chemistry Page 8 Q 3.You are provided with only one alkali calcium hydroxide. Two white salts sodium chloride and ammonium chloride are given. How can you identify them? 10-chemistry Page 9

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