\n1000 atms.<\/td>\n | 400\u00b0C<\/td>\n | 79.8%<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n (iv) Purity of Gases : Any kind of impurity tends to slow down the reaction or poisons catalyst. So, the gases that are to be used should be pure and dry.<\/p>\n Question 5:<\/strong> (i) What are the products formed when ammonia is oxidised with copper oxide ? \n(ii) What is the difference between chemical nature of an aqueous solution of hydrogen chloride and an aqueous solution of ammonia. . \nAnswer:<\/strong> (i) Nitrogen, copper and water. \n(ii) Aqueous solution of HCl is acidic while aqueous solution of ammonia is basic.<\/p>\nQuestion 6:<\/strong> How would you prepay : \n(i) Nitrogen from ammonia. (ii) Ammonia from nitrogen. \n(iii) Nitric oxide gas and nitrous oxide gas. \nAnswer:<\/strong> (i) Ammonia gas bums in the presence of oxygen in a glass jar with a greenish yellow flame to form nitrogen and steam. \n4NH3<\/sub> + 3O2<\/sub>\u00a0 \u27f6 \u00a02N2<\/sub> + 6H2<\/sub>O \n(ii) Nitrogen combines with heated metals; for example, aluminium to form aluminium nitride, which is readily decomposed by water to form ammonia gas which has a characteristic pungent odour and aluminium hydroxide is also formed. \n \n(iii) Introduce the given gas in the atmosphere of oxygen and if reddish brown fumes are produced, then the given sample of gas is nitric oxide and if no brown fumes are produced and the mixture remains colourless, then the gas is nitrous oxide.<\/p>\nQuestion 7:<\/strong> Outline the conditions of the synthetic process for producing ammonia gas. Mention the catalyst used. \nAnswer:<\/strong> A mixture of nitrogen and hydrogen in the ratio of 1 : 3 by volume is passed over heated iron at 450\u00b0C in the presence of molybdenum, which acts as catalyst (promoter) under 200 atmospheric pressure. The reaction of nitrogen and hydrogen is a reversible reaction hence ammonia is removed from the reaction vessel from time to time by liquefaction under high pressure, so that the reaction proceeds in the forward direction. \n<\/p>\nQuestion 8:<\/strong> Name one element in each case, to which the following description would apply. \n(i) The burning metal which combines directly with nitrogen. \n(ii) Define fixation of nitrogen and state two ways in which fixation of nitrogen occurs, naturally. \n(iii) Give two reasons to show that the solution of ammonia in water contains hydroxide ions. \nAnswer:<\/strong> (i) Magnesium, calcium and aluminium. \n(ii) Conversion of atmospheric nitrogen into soluble nitrogenous Compounds which can be easily absorbed by the roots of the plants. \n(a) During thunder and lightning \n(b) By symbiotic bacteria \n(iii) (a) It turns red litmus solution to blue. \n(b) It reacts with adds to form salt and water.<\/p>\nQuestion 9:<\/strong> (i) Of the two gases, ammonia and hydrogen chloride, which is more dense ? Name the method of collection of this gas. \n(ii) Give one example of a reaction between the above two gases which produces a solid compound. \nAnswer:<\/strong> (i) HCl collected by upward displacement of air \n(ii) NH3<\/sub> + HCl\u00a0 \u27f6 \u00a0NH4<\/sub>Cl<\/p>\nQuestion 10:<\/strong> (i) Does ammonia bum in oxygen ? If yes, give equation. \n(ii) What is catalytic oxidation of ammonia ? \n(iii) What is the special feature of the apparatus that is used in the laboratory preparation of nitric acid ? \n(iv) Why should the temperature of the reaction mixture of nitric acid not be allowed to rise above 200\u00b0C ? \nAnswer:<\/strong> (i) Yes. Ammonia bums in oxygen with a greenish yellow flame producing water vapour and nitrogen. \n4NH3<\/sub> + 3O2<\/sub> \u00a0\u27f6 \u00a02N2<\/sub> + 6H2<\/sub>O \n(ii) Ammonia, when reacts with oxygen in presence of platinum (as catalyst) at 800\u00b0C, ammonia is oxidised to nitric oxide (NO). This is called catalytic oxidation of ammonia. \n(iii) It is an all glass retort. \n(iv) Because above 200\u00b0C nitric acid will decompose.<\/p>\nQuestion 11:<\/strong> Oxidation of ammonia under certain conditions is represented by the following equation. \n4NH3<\/sub> + 5O2<\/sub>\u00a0 \u27f6 \u00a04NO + 6H2<\/sub>O \n(i) Give the conditions required for this reaction. \n(ii) Briefly describe the importance of this reaction in industry. \nAnswer:<\/strong> (i) Pure and dry ammonia gas mixed with air in the ratio of 1 : 8 by volume is first compressed and then passed over heated platinum gauze at 800\u00b0C. \n(ii) Nitric oxide is obtained by the oxidation of ammonia, which is further oxidised to form nitrogen dioxide. Nitrogen dioxide is dissolved in water, in the presence of oxygen, to form nitric acid. Thus, nitric acid can be prepared by the catalytic oxidation of ammonia. \n<\/p>\nhttps:\/\/www.youtube.com\/watch?v=4rDC-7zs88I<\/p>\n Question 12:<\/strong> (i) What would you see during burning of ammonia in oxygen. \n(ii) Name the catalyst used in the catalytic oxidation of ammonia. \n(iii) In the reaction of the catalytic oxidation of ammonia the catalyst glows red hot, Why ? \n(iv) What is the name of the industrial process, which starts with the reaction of catalytic oxidation of ammonia. \n(v) How is the temperature maintained in the Ostwald’s process ? \nAnswer:<\/strong> (i) The bunting of ammonia in oxygen produces a bluish green flame. The reaction is irreversible and highly exothermic. \n(ii) Platinum. \n(iii) The catalyst glows red hot without external heating because much heat is liberated during the reaction. \n(iv) Ostwald’s process. \n(v) In the Ostwald’s process, the catalytic oxidation of ammonia to nitric oxide is an exothermic reaction. Once the reaction starts, the heat released maintains the temperature of the catalyst.<\/p>\nQuestion 13:<\/strong> (i) How would you obtain the compound magnesium nitride ? \n(ii) What property of ammonia is illustrated by the reaction between ammonia and copper oxide. \n(iii) What important industrial process starts with reaction between ammonia and oxygen. Name the catalyst uses. \n(iv) During laboratory preparation how is ammonia dried and collected ? \nAnswer:<\/strong> (i) By burning magnesium in the atmosphere of nitrogen by direct combination of elements. \n3Mg + N2<\/sub> \u00a0\u27f6 \u00a0Mg3<\/sub>N2<\/sub> \n(ii) Reducing property of Ammonia, as it reduces CuO to Cu in reaction. \n(iii) Ostwald process for the manufacture of nitric acid and the catalyst used is platinum gauze. \n(iv) Ammonia is dried by passing it through quick lime (CaO) and is collected by downward displacement of air.<\/p>\nQuestion 14:<\/strong> (i) Give the balanced equations for laboratory preparation of nitric acid and describe the reaction. \n(ii) In laboratory preparation of nitric acid, the mixture of potassium nitrate and concentrated sulphuric add should not be heated above 200\u00b0C. Explain ? \nAnswer:<\/strong> (i) In laboratory, nitric acid is prepared by heating potassium nitrate with concentrated sulphuric acid at low temperature, potassium hydrogen sulphate and nitric acid are formed, and at a higher temperature, potassium sulphate and nitric add are formed. \nLow temp. \n \n(ii) In laboratory preparation of nitric acid, the mixture of potassium nitrate and concentrated sulphuric acid should not be heated above 200\u00b0C because at a higher temperature, potassium sulphate is formed. Potassium sulphate is deposited as a hard, solid mass in the retort, which is difficult to remove. Moreover, most of the nitric acid decomposes at a higher temperature to form reddish brown fumes of nitrogen dioxide and the acid acquire a yellow colouration.<\/p>\nQuestion 15:<\/strong> (i) (a) What compounds are required for the laboratory preparation of nitric acid ? \n(b) The first step in the manufacture of nitric acid is the catalytic oxidation of ammonia. What is the name of the catalyst ? \n(ii) (a) How soluble is ammonia in water ? \n(b) Give two reasons to show that the solution of ammonia in water contains hydroxide ions. \n(c) Name a simple method you would employ to prepare ammonium salts in your laboratory. \nAnswer:<\/strong> (i) (a) Nitre (Potassium Nitrate) and cone, sulphuric acid. \n(b) Platinum. \n(ii) (a) Extremely soluble. \n(b) Ammonia solution in water turns red litmus blue and phenolphthalein pink. Ferric chloride, aluminium chloride solutions treated with ammonia solution give precipitates of Fe(OH)3<\/sub> and Al(OH)3<\/sub> respectively. \n \n(c) By titration or neutralisation.<\/p>\nQuestion 16:<\/strong> (i) Among the elements chlorine, nitrogen and sulphur select: \n(a) The least reactive. (b) Obtained from the atmosphere. \n(ii) Why commercial nitric acid is brown ? \n(iii) How can you get ‘liquid air’ ? \nAnswer:\u00a0<\/strong>(i) (a) Nitrogen. (b) Nitrogen. \n(ii) Commercial nitric acid is brown in colour because it contains dissolved nitrogen dioxide. \n(iii) CO2<\/sub> and moisture-free air is passed through a condenser. Finally, this air is compressed, cooled and suddenly allowed to expand. By repeating this process, the air can be liquified.<\/p>\nQuestion 17:<\/strong> Give two reactions to show that nitric acid is : \n(i) An acid. \n(ii) An oxidizing agent. \nAnswer:<\/strong> (i) (a) Dilute nitric acid reacts with magnesium metal to liberate hydrogen gas and magnesium nitrate is formed. \nMg + 2NHO3<\/sub> \u00a0\u27f6 \u00a0Mg(NO3<\/sub>)2<\/sub> + H2<\/sub> \u2191 \n(b) Dilute nitric acid reacts with marble pieces to liberate carbon dioxide gas and calcium nitrate is formed. \nCaCO3<\/sub> + 2HNO3<\/sub> \u00a0\u27f6 \u00a0Ca(NO3<\/sub>)2<\/sub> + H2<\/sub>O + CO2<\/sub> \u2191 \n(ii) (a) When carbon is heated with concentrated nitric acid, it is oxidized to carbonic add and the acid is reduced to nitrogen dioxide and water. \nC + 4HNO3<\/sub> \u00a0\u27f6 \u00a0H2<\/sub>CO3<\/sub> + 4NO2<\/sub> + H2<\/sub>O \n(b) When sulphur is heated with concentrated nitric acid, it is oxidized to sulphuric acid and the nitric’add is reduced to nitrogen dioxide and water. Carbonic add further decomposes to carbon dioxide. \nS + 6HNO3<\/sub> (Conc) \u00a0\u27f6 \u00a0H2<\/sub>SO4<\/sub> + 6NO2<\/sub> + 2H2<\/sub>O<\/p>\nQuestion 18:<\/strong> In what way does the action of dilute nitric acid on a metal like zinc differ from the action of dil. sulphuric acid. Or \nDilute Nitric acid is generally considered a typical add except for its reaction with metals. In what way is dilute Nitric acid different from other acids when it reacts with metals ? \nAnswer:<\/strong> Nitric add is a strong oxidising agent and oxidises the liberated hydrogen to water and is itself reduced to nitrogen dioxide. On the other hand dilute sulphuric acid can not oxidise the liberated hydrogen to water.<\/p>\nQuestion 19:<\/strong> The reaction of nitric acid with metals depends upon the concentration of the acid. Give examples, alongwith equations to illustrate the reaction of the add. \nAnswer:<\/strong> Copper reads differently with nitric add at different concentrations and temperature. \n(i) Copper reacts with cold and dilute nitric add to form copper nitrate, water and nitric oxide gas is liberated. \n \n(ii) Copper reacts with hot and concentrated nitric acid to form copper nitrate, water and nitrogen dioxide.gas, which has reddish brown fumes and a pungent smell is liberated. \n<\/p>\nQuestion 20:<\/strong> Answer the questions given below, relating your answer only to compounds given in the following list: \nTetrammine copper (II) sulphate, Iron (III) chloride, cone. Nitric add, Ammonium hydroxide. \n(i) Write name of the colours and action when concentrated nitric acid is heated with copper turnings ? \n(ii) A compound X is dissolved in the ammonia solution to give a deep blue coloured solution, write the name of the compound having deep blue colours ? \n(iii) The concentrated nitric acid produces yellow stains and blisters on skin. Give the reason. \nAnswer:<\/strong> (i) Brown fumes of nitrogen dioxide are evolved. \n(ii) Tetrammine copper (II) sulphate. \n(iii) This is due to the chemical reaction that occurs between nitric acid and proteins of skin and flesh. In this reaction, a complex compound xanthoprotic acid is formed.<\/p>\nQuestion 21:<\/strong> The action of heat on the blue crystalline solid L gives a reddish brown gas M, a gas which relights a glowing splint and leaves a black residue. When as N, which has a rotten egg smell, is passed through a solution of L a black precipitate is formed. \n(i) Identify L, M and N (Name or formula). \n(ii) Write the equation for the action of heat on L. \n(iii) Write the equation for the reaction between the solution of L and the gas N. \nAnswer:<\/strong> (i) L is copper nitrate. \nM is nitrogen dioxide gas. \nN is hydrogen sulphide gas. \n<\/p>\nQuestion 22:<\/strong> How will you show that nitric arid contains : \n(i) Hydrogen (ii) Nitrogen (iii) Oxygen ? \nAnswer:<\/strong> (i) Dilute nitric acid reacts with magnesium metal to liberate hydrogen gas which bums with a pale blue flame and a pop sound and magnesium nitrate is formed. \nMg + 2HNO3 <\/sub>(Dil) \u00a0\u00a0\u27f6 \u00a0Mg(NO3<\/sub>)2<\/sub> + H2 <\/sub>\u2191 \n(ii) Nitric arid when heated with copper turnings, produces brown fumes of nitrogen dioxide, which are passed over red hot iron filings. The residual gas collected over water is nitrogen. \n \n(iii) Nitric arid, when heated alone, is decomposed into a reddish brown coloured gas nitrogen dioxide, steam and a colourless, odourless gas oxygen, which rekindles a glowing splinter. \n4HNO3 \u00a0\u00a0<\/sub>\u27f6 \u00a04NO2<\/sub> + 2H2<\/sub>O + O2<\/sub><\/p>\nQuestion 23:<\/strong> What is the ring test for nitric acid ? Briefly describe this test. \nAnswer:<\/strong> To the nitrate solution, add freshly prepared iron (II) sulphate solution. Filter off the precipitate if formed. Now carefully add cone. H2<\/sub>SO4<\/sub> along the sides of the test tube. A dark , brown ring is formed at junctions of two liquids. Brown ring is due to the formation of \nnitrosonium pentaqua iron (I) sulphate [Fe+<\/sup> (NO+<\/sup>) (H2<\/sub>O)5<\/sub>] SO4<\/sub>, which is an octahedral complex compound.<\/p>\nQuestion 24:<\/strong> Gas B turns moist red litmus paper blue. \n(i) What is the name of gas B ? \n(ii) Write the equation for the reaction that takes place when gas B is passed over- heated copper oxide. \nAnswer:<\/strong> (i) Gas B is ammonia. \n(ii) 3CuO + 2NH3<\/sub>\u00a0\u00a0\u27f6<\/strong> \u00a03Cu + 3H2<\/sub>O + N2<\/sub> \u2191<\/strong><\/p>\nQuestion 25:<\/strong> (i) Sodium hydroxide solution is added to solution A, a white precipitate is formed which is soluble in excess of sodium hydroxide. What metal ion is present in A ? \n(ii) Ammonium hydroxide solution is added to solution B, when a pale blue precipitate is formed. This pale blue precipitate dissolves in excess of ammonium hydroxide to give inky blue colouration. Name the cation present in B. Name the probable colour of solution B. \n(iii) When an ammonium salt is warmed with sodium hydroxide solution, ammonia gas is evolved. State three ways in which you can identify the gas. \nAnswer:<\/strong> (i) Ammonium ion is present in A. \n(ii) The cation present in B is copper. Solution B is blue in colour. \n(iii) The three ways in which the gas can be identified are as follows : \n(a) It gives dense white fumes when a rod dipped in HCl is held in it. \n(b) It turns moist red litmus paper blue. \n(c) It turns phenolphthalein solution pink.<\/p>\nFigure\/Table Based Questions<\/span><\/h3>\nQuestion 1:<\/strong> \n \n(i) Name (a) the ammonium salt A (b) alkaline gas C. \n(ii) How the conversion D is carried out ? State all the conditions like temperature, pressure and catalyst. \n(iii) (a) How is C converted to nitric oxide ? Write the equation. \n(b) What is the name of the process ? \n(c) How is temperature maintained in above process ? \n(d) Write the equation for conversion of F and G. \n(iv) Name the coloured gas and the colourless gas. \nAnswer:<\/strong> (i) (a) Ammonium nitrate, NH4<\/sub>NO3<\/sub> \n(b) Ammonia. \n(ii) D is mixed with hydrogen in the ratio of 1 : 3, compressed to a pressure of 200 to 500 atmosphere and passes over a catalyst (iron) heated to 450 to 500\u00b0C. \n(iii) (a) By passing the gas with excess of air over platinum gauze heated to 800\u00b0C. \n4NH3<\/sub> + 5O2<\/sub> \u00a0\u27f6 \u00a04NO + 6H2<\/sub>O \n(b) Ostwald process. \n(c) The oxidation of ammonia to nitric oxide is exothermic reaction and once the reaction is started it maintains the temperature of the platinum gauze. \n \n(iv) Nitrogen dioxide and oxygen.<\/p>\nQuestion 2:<\/strong> The diagram shows an experimental set up for the laboratory preparation of a pungent smelling gas. The gas is alkaline in nature. \n \n(i) Name the gas collected in the jar. \n(ii) Write the balanced equation for the above preparation. \n(iii) How is the gas being collected ? \n(iv) Name the drying agent used. \n(v) How will you find that the jar is full of gas ? \nAnswer:<\/strong> (i) Ammonia. \n \n(iii) By downward displacement of air. \n(iv) Quick lime (CaO). \n(v) By bringing a wet red litmus paper near the brim (mouth) of the gas jar. When jar is full of gas litmus will turn blue.<\/p>\nQuestion 3:<\/strong> Dry ammonia gas is passed over black substance as shown in figure below : \n \n(i) Name the black substance A. \n(ii) Name the gas evolved B. \n(iii) Write a balanced equation for the reaction of ammonia with A. \n(iv) What do you observe when ammonia is passed over copper oxide ? \n(v) State the property illustrated in the above reaction (iii). \nAnswer:<\/strong> (i) Copper II oxide. \n(ii) Nitrogen gas. \n \n(iv) The black mass changes t0 reddish powdery mass. \n(v) Ammonia is a reducing agent.<\/p>\nQuestion 4:<\/strong> The figure given below illustrates the apparatus used in the laboratory preparation of nitric acid. \n \n(i) Name A (a liquid), B (a solid) and C (a liquid). (Do not give the formulae) \n(ii) Write an equation to show how nitric acid undergoes decomposition. \n(iii) Write the equation for the reaction in which copper is oxidized by concentrated nitric acid. \nAnswer:<\/strong> (i) A-Conc. Sulphuric acid, B-Potassium nitrate or Sodium nitrate, C-Nitric acid \n<\/p>\nQuestion 5:<\/strong> (i) Draw a neat sketch for.the manufacture of ammonia by Haber’s process. \n(ii) Discuss the principles involved in Haber’s process. \nAnswer:<\/strong> (i) \n \n(ii) The principles involved in Haber’s Process are : \nIn this process, a mixture of pure, dry nitrogen and hydrogen in the ratio of 1 : 3 is compressed to a pressure of 200 to 900 atmospheres. The compressed gases are passed over heated catalyst (finally divided molybdenum, i.e. Fe\/Mo) at 450\u00b0 to 500\u00b0C. \n<\/p>\nThe above reaction is exothermic and reversible. It is accompanied by decrease in volume. Ammonia formed is immediately removed from the catalytic chamber and allowed to condense to form liquid ammonia.<\/p>\n Question 6:<\/strong> Study the scheme for dilute nitric acid. \n \n(i) Give the name or formula of \n(a) Solution A \n(b) Solution B \n(c) Acation in solution C \n(d) Solid D \n(ii) What property of nitric acid is shown by its reaction with iron (II) ions and aqueous potassium iodide solution ? \n(iii) Describe one other reaction of dilute nitric acid not shown in the reaction scheme, that is typical of a strong acid. \nAnswer:<\/strong> (i) (a) Copper (II) nitrate Cu(NO3<\/sub>)2<\/sub> \n(b) Ammonium nitrate \n(c) Fe3+<\/sup> \n(d) Iodine \n(ii) Oxidising property of nitric acid. \n(iii) It is a characteristic of strong acids that when dilute, they react with the more electropositive metals, liberating hydrogen gas. \nZn + 2H+<\/sup> \u27f6 \u00a0Zn2+<\/sup> + H2<\/sub> \nThis reaction can not occur with nitric acid as it is a powerful oxidising agent. Any hydrogen initially produced is at once oxidised by more of the acid to water. If however very dilute nitric acid is used (about 1%) with magnesium or manganese, some hydrogen will be produced, escaping oxidation because of the very dilute condition of the acid. \nMg + 2HNO3<\/sub> (very dil.) \u00a0\u27f6 \u00a0Mg(NO3<\/sub>)2<\/sub> + H2<\/sub><\/p>\nQuestion 7:<\/strong> Copy and complete the following table relating to the important industrial process. Output refers to the product of the process and not the intermediate steps.<\/p>\n\n\n\nName of process<\/td>\n | Inputs<\/td>\n | Catalyst<\/td>\n | Equation for catalyst reaction<\/td>\n | Output<\/td>\n<\/tr>\n | \n<\/td>\n | Ammonia + air<\/td>\n | <\/td>\n | <\/td>\n | Nitric add<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Answer:<\/strong> \n \nQuestion 8:<\/strong> Copy and complete the following table relating to important industrial process:<\/p>\n\n\n\nName of the process<\/td>\n | Temperature<\/td>\n | Catalyst<\/td>\n | Equation for the catalyzed reaction<\/td>\n<\/tr>\n | \nHaber’s process<\/td>\n | <\/td>\n | <\/td>\n | <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Answer:<\/strong> \n<\/p>\nReasoning based Questions<\/span><\/h3>\nQuestion 1:\u00a0<\/strong>Ammonia cannot be obtained in laboratory from ammonium nitrate and sodium hydroxide. Why? \nAnswer:<\/strong> This is because ammonium nitrate on heating decomposes explosively with the formation of nitrous oxide and water.<\/p>\nQuestion 2:<\/strong> Why ammonia gas is not collected over water ? \nAnswer:<\/strong> Ammonia gas Is not collected over water because it is highly soluble in water.<\/p>\nQuestion 3:<\/strong> Ammonia cannot be dried by bubbling through concentrated sulphuric acid. Why ? \nAnswer:<\/strong> Ammonia gas cannot be dried by bubbling through concentrated sulphuric acids as it reacts with sulphuric acid to form ammonium sulphate. \n2NH3<\/sub> + H2<\/sub>SO4<\/sub>\u00a0 \u00a0\u2192 \u00a0 \u00a0(NH4<\/sub>)2<\/sub>SO4<\/sub><\/p>\nQuestion 4:<\/strong> Quick lime is the only drying agent used for drying ammonia gas. Why ? \nAnswer:<\/strong> Quick lime is basic in nature and hence does not react with ammonia, which is also basic in nature, whereas all other drying agents are acidic in nature and hence react with ammonia. \n<\/p>\nQuestion 5:<\/strong> Aqueous solution of ammonia gives a pungent smell. Why ? \nAnswer:<\/strong> Aqueous solution of ammonia gives a pungent smell because it is produced due to bacterial decomposition of urea (NH2<\/sub>CONH2<\/sub>), present in urine.<\/p>\nQuestion 6:<\/strong> Ammonia solution is used as laboratory reagent to identify metal ions. Why ? \nAnswer:<\/strong> Ammonium hydroxide can precipitate insoluble hydroxide of metals from their salt solutions. \nThus, it is used in analytical analysis of salts in laboratory.<\/p>\nQuestion 7:<\/strong> Aqueous solution of ammonia turns red litmus blue. Give reason. \nAnswer:<\/strong> This is because ammonia on dissolving in water furnishes ammonium (NH+<\/sup>) ions and hydroxyl (OH–<\/sup>) ions. The presence of OH–<\/sup> ions in the solution turns red litmus blue. \nNH3<\/sub> + H2<\/sub>O\u00a0\u00a0\u21cc \u00a0 NH4<\/sub>+<\/sup> + OH–<\/sup><\/p>\nQuestion 8:<\/strong> Ammonia solution is used to remove oil and grease stains from clothes. Give reason. \nAnswer:<\/strong> When ammonium chloride is heated and rubbed with the metal, the ammonia formed removes grease, oil, etc. It emulsifies fats, grease, etc. \n \nThe hydrogen chloride formed removes the oxides of metals and thus cleans the metal surfaces before soldering, tinning, etc.<\/p>\nQuestion 9:<\/strong> Liquid ammonia is used as refrigerant in ice plants. Give reason. \nAnswer:<\/strong> Liquid ammonia is a refrigerant as it has high latent heat of vaporisation equal to 5700 cals\/mole and a low boiling point. When liquid ammonia evaporates, it takes large amount of heat from surroundings, resulting in the fall in temperature. \n<\/p>\nQuestion 10:<\/strong> During the manufacture of nitric acid by Ostwald’s process excess of oxygen is taken. Give reason. \nAnswer:<\/strong> Excess of oxygen is taken because each and every step requires oxygen.<\/p>\nQuestion 11:<\/strong> In the laboratory preparation of nitric acid, it can be obtained below 200\u00b0C or above 200\u00b0C, but the lower temperature is preferred. Why ? \nAnswer:<\/strong> The lower temperature is favoured due to the following reasons : \n(i) The glass apparatus may break at higher temperature. \n(ii) A significant amount of nitric acid gets decomposed at higher temperature. \n(iii) At higher temperature, potassium or sodium sulphate are formed, which cannot be easily removed from the apparatus.<\/p>\nQuestion 12:<\/strong> Cone. HCl is not used in place of cone. H2<\/sub>SO | | |