MAHESH TUTORIALS I.C.S.E.

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1 ICSE X MAES TUTORIALS I.C.S.E. Marks : 80 Exam No. : MT/ICSE/I SPA 033SUBJECT : CEMISTRY Time : 2 hrs. Topics : Sulphuric acid, Ammonia, Analytical Chemistry, Organic Chemistry Cl, Nitric acid, Metallurgy Model Answer Paper SECTION I (40 Marks) Attempt all questions from this section. A.. (A). (C) Ethyne 2. (D) conc. Sulphuric acid 3. (A) Non-volatile acid 4. (C) Calcium nitride 5. (B) O (B). d) Chalky white soluble in excess 2. c) Dirty green 3. e) Gelatinous white soluble in excess. 4. a) Reddish brown 5. b) Pale blue (C). In the contact process sulphur trioxide vapours does not react with water because the reaction is highly exothermic resulting in production of a dense fog of sulphuric acid particles which do not condense easily. 2. Ammonia is environmentally compatible. It does not deplete ozone layer and does not contribute to global warming. It has superior thermodynamic qualities as a result ammonia refrigeration systems use less electricity. Ammonia has a recognizable odour and so leaks are not likely to escape. 3. Sulphuric acid is a strong oxidising agent, it oxidises hydrogen sulphide gas to sulphur and hence is not used to dry it 4. Ethyne is more reactive than ethane due to the presence of C C carbon - carbon triple bond often referred to as acetylenic linkage. 5. In the esterification reaction, acid reacts with alcohol to give ester and water. This is a reversible reaction. Conc. 2 acts as a dehydrating agent. Reversible reaction may be prevented by using conc. 2 when the reaction is carried to completion by removal of 2 O. (D). (i) Catalytic chamber T7 I SPA 008 4N 3 + 5O 2 Pt 800 o C 4NO O + (2.5 K cals)

2 (ii) Oxidation chamber 2 NO + O 2 50ºC 2NO 2 (iii) Absorption tower 4NO 2 O + O 2 4N 3 2. In catalytic chamber the temperature is maintained at ºC Catalytic oxidation of ammonia is an exothermic process and heating is done initially. As electric heating is stopped temperature stays at ºC due to the heat of the reaction. 3. Oxygen is required in all three reactions in the manufacture. Since, only about 2% by volume of air is oxygen, a higher percentage of air is required in the manufacture of nitric acid. (E). Neutral litmus turns blue in alkaline solution. 2. Ammonia burns with a green or greenish yellow flame. 3. Black spongy mass and colourless gas is evolved. 4. Brown colour of the bromine discharges. 5. Neutral FeCl 3 solution turns wine red. (F). Special funnel arrangement. ydrogen chloride gas Air gap Figure (i) Figure (ii) 2 2. (i) Such an arrangement is necessary because direct absorption of Cl gas in water using a delivery tube causes back suction. (ii) ydrogen chloride gas is extremely soluble in water. If a delivery tube through which Cl gas is passed is directly immersed in water the rate of absorption of Cl gas is high and hence a partial vacuum is created in the tube. The pressure outside being higher causes the water to be pushed up into the delivery tube and damages the apparatus. This is called back-suction. 3. Preparation of ydrogen chloride - 2NaCl + 2 > 200ºC Na 2 + 2Cl T7 I SPA 008

3 (G). 2NaC + 2 (dil) Na 2 O + 2CO 2 2. C (conc.) CO 2 O + 2SO 2 3. N 3 + 3Cl 2(excess) 3Cl + NCl C 3 COO + 2Na 2C 3 COONa CaC 2 O C Ca(O (). C2 Br + 2KO boil C C + 2KBr + 2 O Alcoholic ethene C Br 2, 2 dibromo ethane 2. C 3 C 2 COONa + NaO CaO C Na 2 C Sodium Propionoate Soda lime Ethane C C + 2 O Al 3. 2O3 C C o 350 C O CCl C C 4 4. C C + Cl 2 ethyne inert Cl Cl solvent,2 dichloroethene 5. C 2 5 O + C 3 COO conc. SO 2 4 C 3 - COO - C O Ethanol Ethanoic acid Ethyl acetate SECTION II (40 Marks) Attempt any four questions from this section. A.2 (A). A : 2N 4 O + 2 (dil.) (N 4 O B : (N 4 + 2NaO Na 2 O + 2N 3 OR (N 4 + Ca(O Ca O + 2N 3 2. C : N 3 + Cl (dil) N 4 Cl D : 8N 3(excess) + 3Cl 2 6N 4 Cl + N 2 (B). A white precipitate is formed which gets dissolved on heating. 2. Effervescence are seen which turns lime water milky but has no effect on KMnO 4 solution. 3. Yellow particles are seen. T7 I SPA 008

4 (C). Thermit is a mixture of 3 parts of ferric oxide and one part of aluminium powder. 2. Ignition mixture is a mixture of potassium chlorate and magnesium powder. 3. Fe 2 + 2Al Al 2 + 2Fe + eat A.3 (A). C. Pig iron 2. A. Lead metal 3. B. Brass 4. E. Duralumin 5. D. Stainless steel (B) Catenation is the property of elements by virtue of which atoms of the element can link to each other in the form of chains of identical atoms. (C). C C 2. alogenation reaction (Addition reaction) 3. Ethanol 4. Reaction with excess conc. 2 at 70 o C causes dehydration of ethyl alcohol to give ethene. C 2 5 O Conc. 2 C 70 O 2 C O C A.4 (A). It is because it does not liberate hydrogen on reaction with metals. Nitric acid is a powerful oxidising agent and the nascent oxygen formed on decomposition oxidises the hydrogen to water. 2. Pure nitric acid is colourless and unstable and decomposes slightly even at ordinary temperatures and in presence of sunlight. The decomposition results in formation of reddish brown nitrogen dioxide which remains dissolved in the acid thus imparting a slight yellowish brown colour. 3. Nitric acid vapours are highly corrosive in nature and may corrode rubber cork, but does not affect glass, hence the apparatus used in laboratory preparation is all glass apparatus. 4. NO 2 combines with water to form 2 acids - nitrous acid & nitric acid. Thus it is called a mixed acid anhydride. 2NO O N + NO 2 T7 I SPA 008

5 (B). Pure acid is not acidic in nature as pure acid does not dissociate producing + ions, which in turn does not produce 3 O + ions, which gives acidic nature. But upon dilution, acid dissociates producing + ions, which in turn produces 3 O + ions. ence acid when dilute behaves as an acid. 2. Sulphuric acid dissociates in aqueous solution giving 2 + ions per molecule of the acid. Sulphuric acid forms two types of salts with an alkali, an acid salt and a normal salt. (C). NaCl + 2 o 200 C Na + Cl Fe + 2Cl FeCl Cl + N 3 N 4 Cl 4. Pb(N + 2Cl PbCl 2 + 2N A.5 (A). C 3 O C 3 O 2. C 3 C C 2 C 2 C 3 3. C 3 C 2 COO (B). The reactants used are nitrogen and hydrogen. 2. Pure nitrogen is obtained by fractional distillation of liquid air. Pure hydrogen is obtained from water gas by Bosch process. 3. N o C atm 2N 3 Fe, Mo + 22,400 cals. (C). (i) Al O + 2NaO 50º- 200ºC 2NaAlO O Impure Sodium bauxite aluminate (ii) NaAlO 2 O 50º- 60ºC NaO + Al(O) 3 (iiial(o) 3 00ºC Al O (Vap.) Pure Alumina 2. Fluorspar and cryolite act as a solvent. The percentage by weight composition is as follows. Alumina : 20%, Cryolite : 60% and Fluorspar : 20% T7 I SPA 008

6 A.6 (A). Butene 2. C C C C C C Pt (B). 4N 3 + 5O 2 o 4NO C 2 O + Nitric oxide 2. White to Blue 3. Acidic oxide (C) (i) Flux : The substances added to the ore to get rid of the matrix (earthly impurities) resulting in the formation of a fusible compound slag. (ii) Ore : The naturally occuring minerals from which metals can be extracted profitably and conveniently are called ores. (iii) Smelting : Smelting is the process of reducing the roasted oxide ore and removing the gangue with the help of an appropriate flux added with the ore. It reduces the oxide ore to metals in the molten condition. A.7 (A). C: ydrogen 2. A: Nitrogen dioxide only 3. B: Nitric oxide only 4. E: Nitrogen dioxide with carbon dioxide (B). C 2 2 is an alkyne with general formula C n 2n 2 (n = 2) C 5 0, C 6 2, C 4 8 are alkenes with general formula C n 2n [n = 5, n = 6, n = 4] 2. Carbonic acid Carbonic acid is a weak acid whereas others are strong acid. (C). Ethene, ethyne 2. Acetic acid 3. Ethyne, ethene 4. Ethanol T7 I SPA 008

ICSE-Science 2 (Chemistry) 2004

ICSE-Science 2 (Chemistry) 2004 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