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This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
The following questions are based on the preparation of ammonia gas in the laboratory:1. Explain why ammonium nitrate is not used in the preparation of ammonia.2. Name the compound normally used as a drying agent during the process.3. How is ammonia gas collected ? Explain why it is not collected over water. |
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Answer» 1. Ammonium nitrate does not undergo a reversible sublimation reaction, it melts and then decompses into nitrogen oxide gas and water vapour. Thus it is not used in the preparation of ammonia. NH4NO3 → N2O + 2H2O 2. Calcium oxide 3. Ammonia is collected in an inverted dry gas jar by downward displacement of air. It is highly soluble in water and hence cannot be collected by downward displacement of water. |
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| 2. |
Give the word equation and balanced molecular equation for the laboratory preparation of ammonia from NH4Cl and calcium hydroxide. |
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Answer» Ammonium Chloride + Calcium Hydroxide → Calcium Chloride + Water + Ammonia. 2NH4Cl + Ca(OH)2 → CaCl2 + 2H2O + 2NH3 |
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| 3. |
Write a balanced chemical equation to illustrate the reducing nature of ammonia. |
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Answer» Reducing nature of ammonia. 2NH3 + 3CuO → 3Cu + 3H2O+ N2(g) |
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| 4. |
State five tests for ammonia where a colour change is involved. |
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Answer» Tests for ammonia : 1. Ammonia turns red (or purple) litmus solution to blue. 2. Ammonia turns methyl orange solution to yellow. 3. Ammonia turns phenolphthalein (colourless) solution to pink. 4. Ammonia turns Nesseler’ reagent (colourless) solution to pale brown. 5. Ammonia (when in excess) gives a deep blue coloured solution with CuSO4 (aq.) |
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| 5. |
Write balanced equations for :1. Action of warm water on AIN.2. Excess of ammonia is treated with chlorine.3. An equation to illustrate the reducing nature of ammonia. |
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Answer» (i) AIN + 3H2O → AI(OH)3 + NH3 (ii) 8NH3 + 3Cl2 → 6NH4Cl + N2 (iii) 3CuO + 2NH3 → 3Cu + N2 + 3H2O |
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| 6. |
State two different methods of preparing NH4Cl using hydrochloric acid. |
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Answer» 1. When ammonium hydroxide is treated with hydrochloric acid, neutrilisation reaction takes place with formation of Ammonium chloride NH4OH + HCl (dil.) → NH4Cl + H2O 2. When ammounium carbonate is treated with hydrochloric acid, it forms ammonium chloride, carbon dioxide and water. (NH4)2 CO3 + 2HCl (dil.) → 2NH4Cl + CO2 + H2O |
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| 7. |
State a reason why reaction of liquor ammonia with nitric acid is a neutralization reaction. |
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Answer» Liquor ammonia is a saturated solution of ammonia in water. Ammonia, NH3 dissolves in water to give ammonium hydroxide which dissociates partially to give NH4+ and OH– ions. Due to presence of OH– ions, ammonium hydroxide acts as an alkali. NH3(aq) + H2O (l) → NH4OH(aq) NH4OH(aq) ⇋ NH4+(aq) + OH-(aq) The reaction between an acid (nitric acid) and an alkali or base is a neutralisation reaction. NH4OH(aq) + HNO3(aq) → NH4NO3(aq) + H2O(l) Hence, the reaction between liquor ammonia and nitric acid is a neutralisation reaction. |
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| 8. |
Convert (i) ammonia (ii) ammonium hydroxide to an ammonium salt using(a) HNO3(b) H2SO4 . |
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Answer» (i) From ammonia NH3 + HNO3 → NH4NO3 2NH3 + H2SO4 → (NH4)2SO4 (ii) From ammonia hydroxide NH4OH + HNO3 → NH4NO3 + H2O 2NH4OH + H2SO4 → (NH4)2SO4 + 2H2O |
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| 9. |
What compounds are required for the laboratory preparation of nitric acid ? |
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Answer» Nitre (Potassium Nitrate) and cone, sulphuric acid. |
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| 10. |
How soluble is ammonia in water ? |
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Answer» Extremely soluble. |
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| 11. |
When an ammonium salt is warmed with sodium hydroxide solution, ammonia gas is evolved. State three ways in which you can identify the gas. |
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Answer» The three ways in which the gas can be identified are as follows : (a) It gives dense white fumes when a rod dipped in HCl is held in it. (b) It turns moist red litmus paper blue. (c) It turns phenolphthalein solution pink. |
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| 12. |
Study the scheme for dilute nitric acid.(i) Give the name or formula o(a) Solution A (b) Solution B(c) Acation in solution C(d) Solid D(ii) What property of nitric acid is shown by its reaction with iron (II) ions and aqueous potassium iodide solution ?(iii) Describe one other reaction of dilute nitric acid not shown in the reaction scheme, that is typical of a strong acid. |
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Answer» (i) (a) Copper (II) nitrate Cu(NO3)2 (b) Ammonium nitrate (c) Fe3+ (d) Iodine (ii) Oxidising property of nitric acid. (iii) It is a characteristic of strong acids that when dilute, they react with the more electropositive metals, liberating hydrogen gas Zn + 2H+ ⟶ Zn2+ + H2 This 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. Mg + 2HNO3 (very dil.) ⟶ Mg(NO3)2 + H2 |
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| 13. |
Name a simple method you would employ to prepare ammonium salts in your laboratory. |
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Answer» By titration or neutralisation. |
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| 14. |
In what way does the action of dilute nitric acid on a metal like zinc differ from the action of dil. sulphuric acid. |
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Answer» 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. |
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| 15. |
Give two reactions to show that nitric acid is :(i) An acid.(ii) An oxidizing agent |
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Answer» (i) (a) Dilute nitric acid reacts with magnesium metal to liberate hydrogen gas and magnesium nitrate is formed. Mg + 2NHO3 ⟶ Mg(NO3)2 + H2 ↑ (b) Dilute nitric acid reacts with marble pieces to liberate carbon dioxide gas and calcium nitrate is formed. CaCO3 + 2HNO3 ⟶ Ca(NO3)2 + H2O + CO2 ↑ (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. C + 4HNO3 ⟶ H2CO3 + 4NO2 + H2O (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. S + 6HNO3 (Conc) ⟶ H2SO4 + 6NO2 + 2H2O |
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| 16. |
How can you get ‘liquid air’ ? |
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Answer» CO2 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. |
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| 17. |
Why commercial nitric acid is brown ? |
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Answer» Commercial nitric acid is brown in colour because it contains dissolved nitrogen dioxide. |
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| 18. |
Aluminium does not react with nitric acid of any concentration. Why ? |
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Answer» Aluminum metal is not attacked by nitric acid of any concentration because of the thin and unreactive protective layer of aluminum oxide formed on the metallic surface due to the reaction of aluminium metal with oxygen of air. |
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| 19. |
Among the elements chlorine, nitrogen and sulphur select:(a) The least reactive.(b) Obtained from the atmosphere. |
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Answer» (a) Nitrogen. (b) Nitrogen |
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| 20. |
Nitrogen obtained from air is more dense as compared to nitrogen obtained from chemicals. Why ? |
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Answer» Nitrogen obtained from air contains traces of inert gases and therefore, it is more dense as compared to chemical nitrogen. |
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| 21. |
Give one example of a reaction between the above two gases which produces a solid compound. |
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Answer» NH3 + HCl ⟶ NH4Cl |
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| 22. |
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.(i) Identify L, M and N (Name or formula).(ii) Write the equation for the action of heat on L.(iii) Write the equation for the reaction between the solution of L and the gas N. |
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Answer» (i) L is copper nitrate. M is nitrogen dioxide gas. N is hydrogen sulphide gas. (ii) 2Cu(NO3)2 → 2CuO + 4NO2 + O2 (iii) Cu(NO3)2 + H2S → CuS + 2HNO3 |
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| 23. |
In Haber’s process before the gases are allowed to enter the oxidation chamber, the gases are sufficiently cooled. Why ? |
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Answer» The gases are cooled so that the complete oxidation of nitric oxide takes place or the rate of forward reaction increases or to minimize the decomposition of nitrogen dioxide. |
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| 24. |
The questions below are related to the manufacture of ammonia.(i) Name the process.(ii) In what ratio must the reactants be taken ?(iii) Name the catalyst used.(iv) Give the equation for the manufacture of ammonia.(v) Ammonia can act as a reducing agent — write a relevant equation for such a reaction. |
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Answer» (i) Haber’s process. (ii) Nitrogen one part, hydrogen three parts. (iii) Iron powder. (iv) N2 + 3H2 → 2NH3 (v) NH3 + 3CuO(copper oxide) → 3Cu(copper) + 3H2O + N2 |
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| 25. |
Why should the temperature of the reaction mixture of nitric acid not be allowed to rise above 200°C ? |
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Answer» Because above 200°C nitric acid will decompose. |
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| 26. |
What would you see during burning of ammonia in oxygen. |
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Answer» The bunting of ammonia in oxygen produces a bluish green flame. The reaction is irreversible and highly exothermic. |
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| 27. |
Outline the conditions of the synthetic process for producing ammonia gas. Mention the catalyst used. |
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Answer» A mixture of nitrogen and hydrogen in the ratio of 1 : 3 by volume is passed over heated iron at 450°C 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. N2 + 3H2 ⇋ 2NH3(Ammonia) + 22 kcal |
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| 28. |
During the manufacture of nitric acid by Ostwald’s process excess of oxygen is taken. Give reason. |
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Answer» Excess of oxygen is taken because each and every step requires oxygen. |
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| 29. |
What are the necessary conditions for getting maximum yield of ammonia ? |
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Answer» The necessary conditions for getting maximum yield of ammonia are as follows : (i) Low Temperature : As the reaction is exothermic in nature, so the temperature should be low. When temperature is lowered, the rate of the reaction slows down and the yield is maximum. It is found for maximum yield, temperature should be between 450° to 500°C (optimum temperature). (ii) Catalyst : A catalyst is used to accelerate the reaction at optimum temperature. Following are the catalysts used: (a) Finely divided iron, mixed with molybdenum as promoter. (b) A better catalyst is ferric oxide (Fe2O3 ) containing 1% of potassium oxide (K2O) and 3% of aluminium oxide (Al2O3 ) which acts as promoters. (iii) High Pressure : When 4 volumes of a mixture of nitrogen and hydrogen are reduced to 2 volumes of ammonia, the pressure drops. In order to have maximum yield the pressure should be very high. The optimum pressure should be between 200 atmospheres to 900 atmospheres.
(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. |
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| 30. |
What are the products formed when ammonia is oxidised with copper oxide ? |
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Answer» Nitrogen, copper and water. |
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| 31. |
In the reaction of the catalytic oxidation of ammonia the catalyst glows red hot, Why ? |
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Answer» The catalyst glows red hot without external heating because much heat is liberated during the reaction. |
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| 32. |
What is the difference between chemical nature of an aqueous solution of hydrogen chloride and an aqueous solution of ammonia. . |
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Answer» Aqueous solution of HCl is acidic while aqueous solution of ammonia is basic. |
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| 33. |
Aqueous solution of ammonia turns red litmus blue. Give reason |
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Answer» This is because ammonia on dissolving in water furnishes ammonium (NH+ ) ions and hydroxyl (OH– ) ions. The presence of OH– ions in the solution turns red litmus blue. NH3 + H2O ⇋ NH4+ + OH- |
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| 34. |
Aqueous solution of ammonia gives a pungent smell. Why ? |
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Answer» Aqueous solution of ammonia gives a pungent smell because it is produced due to bacterial decomposition of urea (NH2CONH2 ), present in urine. |
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| 35. |
How is ammonia collected. Why is ammonia not collected over water. |
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Answer» Ammonia gas is lighter than air and hence collected by the downward displacement of air. Ammonia is not collected over water because it is highly soluble in water. |
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| 36. |
Name : An alkaline gas A which gives dense white fumes with hydrogen chloride. |
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Answer» NH3 (Ammonia) |
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| 37. |
Name a gas whose solution in water is alkaline. |
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Answer» Ammonia (NH3) |
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| 38. |
How would you obtain the compound magnesium nitride ? |
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Answer» By burning magnesium in the atmosphere of nitrogen by direct combination of elements. 3Mg + N2 ⟶ Mg3N2 |
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| 39. |
Fill in the blank from the choices given in bracket :Ammonia gas is collected by _____ (upward displacement of air, a downward displacement of water, a downward displacement of air) |
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Answer» Ammonia gas is collected by a downward displacement of air |
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| 40. |
Rewrite the correct statement with the missing word/s Magnesium nitride reacts with water to liberate ammonia. |
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Answer» Magnesium nitride reacts with warm water to liberate ammonia along with magnesium hydroxide. |
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| 41. |
Write the equation for the formation of ammonia by the action of water on mangesium nitride. |
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Answer» Mg3N2 + 6H2O → 2NH3 + 3Mg (OH)2 |
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| 42. |
Nitrogen gas can be obtained by heating :(a) Ammonium nitrate(b) Ammonium nitrite(c) Magnesium nitric(d) Ammonium chloride |
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Answer» (b) Ammonium nitrite |
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| 43. |
From the list of substances given— Ammonium sulphate, Lead carbonate, Chlorine, Copper nitrate, Ferrous sulphate — State :A compound which on heating with sodium hydroxide produces a gas which forms dense white fumes with hydrogen chloride. |
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Answer» Ammonium sulphate. |
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| 44. |
Ammonia can be obtained by adding water to : [Select the correct word]A Ammonium chlorideB Ammonium nitriteC Magnesium nitrideD Magnesium nitrate |
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Answer» C Magnesium nitride |
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| 45. |
State two relevant observations for : Ammonium hydroxide solution is added to zinc nitrate solution in minimum quantities and then in excess. |
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Answer» A white gelatin like precipitate of zinc hydroxide is formed which dissolves in excess of ammonium hydroxide. |
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| 46. |
Write balanced equation for : Action of warm water on magnesium nitride. |
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Answer» Action of warm water on magnesium nitride. Mg3N2 + 6H2O → 3Mg(OH)2 + 2NH3 |
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| 47. |
‘Ammonia is highly soluble in water’. Name two other gases showing similar solubility. |
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Answer» The other highly soluble gases in water are : 1. Hydrogen chloride 2. Sulphur trioxide |
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| 48. |
Compare the density of ammonia with that of air. Name two gases lighter than ammonia. |
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Answer» The vapour density of ammonia is 8.5 and that of air is 14.4. The two gases lighter than ammonia are 1. hydrogen 2. helium. |
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| 49. |
State two physical properties of NH3 which enable separation of NH3 from a mixture of NH3 , N2 and H2 |
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Answer» 1. Ammonia liquifies at a pressure 8 atmosphere at -33°C, but not hydrogen and nitrogen. 2. Ammonia is extremely soluble in water, but not hydrogen and nitrogen. |
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| 50. |
State what an aqueous solution of NH3 is called. State how it is prepared giving reasons. |
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Answer» The aqueous solution of ammonia is chemically ammonium hydroxide(NH4OH) (Liquor Ammonia). It is prepared by connecting the delivery tube of the apparatus generating ammonia with an inverted funnel whose rim is just dipping in water contained in beaker. This arrangement provides 1. large surface area for the absorption of ammonia and 2. prevents back suction NH3 + H2O → NH4 OH |
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