Question Bank Ammonia 1. Why nitrogenous matter produces ammonia? State a liquid source of ammonia. Ans. When nitrogenous matter (such as animal and vegetable proteins) decays in the absence of air, the puterfying bacteria on the organic matter in the soil or ammonifying bacteria in organic matter produces ammonia. The liquid source of ammonia is decaying urine of animals. 2. Write a word equation and balanced molecular equation for the laboratory preparation of ammonia from ammonium chloride. [2] Ans. Ammonium chloride + Calcium hydroxide calcium chloride + ammonia + water 2NH 4 Cl + Ca(OH) 2 CaCl 2 + 2NH 3 + 2H 2 O 3. Write chemical equations for preparing ammonia from ammonia sulphate by using two different alkalis. [2] heat Ans. (i) (NH 4 ) 2 SO 4 + 2NaOH Na 2 SO 4 + 2NH 3 + 2H 2 O (ii) (NH 4 ) 2 SO 4 + Ca(OH) 2 4. Why is ammonia not obtained in laboratory from NH 4 NO 3 and NaOH? [2] Ans. Ammonium nitrate on heating decomposes explosively with the formation of nitrous oxide and water. heat CaSO 4 + 2NH 3 + 2H 2 O NH 4 NO 3 5. Name the chemical for drying ammonia. Why the chemicals such as CaCl 2, P 2 O 5 and conc. H 2 SO 4 is not used for drying ammonia. Support your answer by chemical equations. [4] heat N 2 O + 2H 2 O + heat Chemistry Class-X 1 Question Bank
Ans. Calcium oxide (quick lime) is used for drying ammonia. It is because, calcium oxide being basic in nature does not react chemically with ammonia. CaO + H 2 O Ca(OH) 2 Chemicals such as CaCl 2 (anhydrous), P 2 O 5 and conc H 2 SO 4 are not used for drying ammonia, because they react chemically with it as shown in the equation below : (i) CaCl 2 + 8NH 3 CaCl 2.8NH 3 (ii) P 2 O 5 + 3H 2 O + 6NH 3 2(NH 4 ) 3 PO 4 (ii) H 2 SO 4 + 2NH 3 (NH 4 ) 2 SO 4 6. Starting from (i) magnesium, (ii) calcium and (iii) aluminium how can you obtain ammonia gas. Support your answer by chemical equations. [9] Ans. (i) Magnesium is burnt in nitrogen so as to obtain magnesium nitride. 3Mg + N 2 Mg 3 N 2 + heat The magnesium nitride is treated with warm water, so as to obtain ammonia. Mg 3 N 2 + 6H 2 O 3Mg(OH) 2 + 2NH 3 (ii) Calcium is burnt in nitrogen so as to obtain calcium nitride. 3Ca + N 2 Ca 3 N 2 + heat. The calcium nitride is treated with warm water, so as to obtain ammonia. Ca 3 N 2 + 6H 2 O 3Ca(OH) 2 + 2NH 3 (iii) Aluminium is burnt in nitrogen so as to obtain aluminium nitride. 2Al + N 2 2AlN + heat Aluminium nitride is treated with warm water, so as to obtain ammonia. AlN + 3H 2 O Al(OH) 3 + NH 3 Chemistry Class-X 2 Question Bank
7. State two physical properties of ammonia which enable its separation from a mixture of NH 3, H 2 and N 2. [2] Ans. (i) Ammonia liquifies at a pressure 8 atomsphere at 33 C, but not hydrogen and nitrogen. (ii) Ammonia is extremely soluble in water, but not hydrogen and nitrogen. 8. How is density of ammonia compare with air? Name two gases lighter than ammonia. [2] Ans. The vapour density of ammonia is 8.5 and that of air is 14.4. The two gases lighter than ammonia are (i) hydrogen (ii) helium. 9. Ammonia gas is highly soluble in water. Name two more gases showing similar solubility. [1] Ans. The other highly soluble gases in water are : (i) Hydrogen chloride (ii) Sulphur trioxide. 10. Write a balanced equation for the burning of ammonia in oxygen and state your observations. [2] Ans. Ammonia burns in the atmosphere of oxygen with a pale blue flame, forming nitrogen gas and water vapour. 4NH 3 + 3O 2 11. By stating all experimental conditions write an equation for the conversion of ammonia into nitric oxide. [2] Ans. When a mixture of 2 (vols.) of oxygen and 1(vols.) of ammonia is passed over platinum gauze maintained at 800 C, it reacts to form nitric oxide and water vapour. burning 2N 2 + 6H 2 O 4NH 3 + 5O 2 12. Name in industrial process which uses a catalyst, ammonia and oxygen as reactants. Ans. The industrial process is called Ostwald s process for preparing nitric acid. Pt 800ºC 4NO + 6H 2 O Chemistry Class-X 3 Question Bank
13. A flask contains 2(vols) of oxygen and 1(vol.) of ammonia. If the flask is lowered a coiled wire of platinum and its ends are connected to a battery through a switch. The flask is sealed and electric current is switched on for 1 minute. Describe your observation and explain by writing balanced chemical equations. Ans. As soon as the platinum coil gets red hot, reddish brown fumes are formed around it. Gradually the whole flask is filled with reddish brown fumes. Reason : Ammonia and oxygen react in the presence of heated platinum (catalyst) to form nitric oxide gas. 4NH 3 + 5O 2 The nitric oxide so formed reacts with oxygen to form nitrogen dioxide gas, which is reddish brown in colour. 2NO + O 2 2NO 2 (reddish brown) 14. What is the chemical name of aqueous solution of ammonia? By giving reasons, explain, how is it prepared? [3] Ans. The aqueans solution of ammonia is chemically ammonium hydroxide. 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 (i) large surface area for the absorption of ammonia and (ii) prevents back suction NH 3 + H 2 O NH 4 OH 15. State why an aqueous solution of ammonia turns red litmus blue? [2] Ans. Ammonia on dissolving in water furnishes ammonium (NH + 4 ) ions and hydroxyl (OH ) ions. Pt 800ºC 4NO + 6H 2 O NH 3 + H 2 O NH 4 + + OH The presence of OH turns the red litmus blue. Chemistry Class-X 4 Question Bank
16. Why is the aqueous solution of ammonia a weak base and weak electrolyte? [2] Ans. When ammonia dissolves in water, it forms ammonium hydroxide. The ammonium hydroxide dissociates to NH + 4 ions and OH ions. However, the degree of dissociation of ammonium hydroxide molecules is very low. Thus, due to the presence of few OH ions it is a weak base, as well as weak electrolyte. 17. By writing chemical equations, explain how can you prepare ammonium chloride from hydrochloric acid by two different methods. [4] Ans. (i) When ammonium hydroxide is treated with hydrochloric acid, neutrilisation reaction takes place with formation of ammonium chloride NH 4 OH + HCl (dil.) NH 4 Cl + H 2 O (ii) When ammounium carbonate is treated with hydrochloric acid, it forms ammonium chloride, carbon dioxide and water. (NH 4 ) 2 CO 3 + 2HCl (dil.) 2NH 4 Cl + CO 2 + H 2 O 18. Write chemical equations for the conversion of : (i) Ammonia to nitric acid. (ii) Ammonium hydroxide to ammonium sulphate. [4] Ans. (i) 1. 4NH 3 + 5O 2 2. 4 NO + O 2 4NO 2 3. 4NO 2 + 2H 2 O + O 2 4HNO 3 (ii) 2NH 4 OH + H 2 SO 4 (NH 4 ) 2 SO 4 + 2H 2 O 19. Write balanced chamical equations for reducing action of ammonia with (i) lead(ii) oxide (ii) excess of chlorine Pt 800ºC 4NO + 6H 2 O heat Ans. (i) 3PbO + 2NH 3 3Pb + 3H 2 O + N 2 (ii) NH 3 + 3Cl 2 NCl 3 + 3HCl Chemistry Class-X 5 Question Bank
20. State five tests for ammonia, where colour change is involved. [5] Ans. (i) It turns red litmus blue. (ii) It turns orange coloured methyl orange solution yellow. (iii) It truns colourless phenolphthalein solution pink. (iv) It forms pale blue ppt. with copper sulphate solution, which dissolves in excess of ammonia to form deep blue colouration. (v) It turns colourless Nesseler s reagent pale brown. 21. State how ammonium hydroxide solution is used in identifying (i) Fe 2+, (ii) Fe 3+, (iii)zn 2+, (iv) Pb 2+ and Cu 2+ ions. Ans. (i) A solution with Fe 2+ ions, forms dirty green ppt. which is insoluble in excess of NH 4 OH. (ii) A solution with Fe 3+ ions, forms reddish brown ppt. which is insoluble in excess of NH 4 OH. (iii) A solution with Zn 2+ ions, forms gelatin white ppt. which dissolves in excess of NH 4 OH to form colourless solution. (iv) A solution with Pb 2+ ions, forms a chalky white ppt. which is insoluble in excess of NH 4 OH. (v) A solution with Cu 2+ ions, forms a bluish white ppt which dissolves in excess of NH 4 OH to form deep blue solution. 22. State the chemical name and formulae of the following salts and a reason for their use : (i) smelling salt (ii) sal ammonic used in dry cells. Ans. (i) Smelling salt is ammonium carbonate [(NH 4 ) 2 CO 3 ]. This salts slowly decompress even at room temperature to release ammonia which gives relief in common cold. (ii) Sal ammonic is ammonium chloride [NH 4 Cl]. This salt is neutral in nature, but reacts with zinc cathode in dry cells to produce electric current. Thus, dry cells do not cause serious damage on leaking. Chemistry Class-X 6 Question Bank
23. Name the gas evolved by choosing from letters A, B, C and D in the following statements. A. N 2 O B. NO C. N 2 D. NO 2 (i) Ammonium nitrite undergoes a thermal decom-position. (ii) A greenish yellow gas reacts with excess of ammonia. (iii) Dry ammonia and oxygen are ignited. (iv) Dry ammonia and oxygen are passed over heated platinum and then allowed to cool. (v) Ammonia gas is passed over heated litharge. [5] Ans. (i) C. N 2 (ii) C. N 2 (iii) C. N 2 (iv) D. NO 2 (v) C. N 2 24. Give balanced equations for the following conversions. [3] NH 4 OH A (NH 4 ) 2 SO 4 B NH 3 C N 2 Ans. A. 2NH 4 OH + H 2 SO 4 (NH 4 ) 2 SO 4 + 2H 2 O B. (NH 4 ) 2 SO 4 + Ca(OH) 2 CaSO 4 + 2NH 3 + 2H 2 O C. 4NH 3 + 3O 2 2N 2 + 6H 2 O 25. Give the balanced equation for the following when E, F and G are different gases. N 2 E NH Cl NH NH Cl F G 4 3 4 Ans. E. 4NH 3 + 3O 2 2N 2 + 6H 2 O F. NH 3 + HCl NH 4 Cl G. 8NH 3 + 3Cl 2 6NH 4 Cl + N 2 [3] Chemistry Class-X 7 Question Bank
26. Select the most probable substance from D, E, F, G and H which must be added to distinguish between: (i) Ammonium sulphate from D. Conc. Hydrochloric ammonium chloride acid. (ii) Potassium sulphate from E. Ammonia gas ammonium sulphate. (iii) Copper (II) oxide F. Sodium hydroxide from Cu(II) chloride (iv) Liquior ammonia G. Barium chloride from liquid ammonia (v) Ammonia and sulphur H. Phenolphthalein dioxide gas. Ans. (i) G. (Barium chloride) (ii) F. (Sodium hydroxide) (iii) E. (Ammonia gas) (iv) H. (Phenolphthalein) (v) D. (conc. hydrochloric acid) 27. Complete the statements by selecting correct word from the brackets. (i) The gas most difficult to liquiefy is [nitrogen/ammonia/hydrogen]. (ii) Ammonia in liquid form is [basic/neutral/acidic]. (iii) The salt solution which gives white ppt. on the addition of ammonium hydroxide solution is [sodium sulphate/potassiam nitrate/magnesium chloride]. (iv) Excess of ammonia reduces chlorine to [NH 4 Cl/ N 2 /HCl]. (v) The alkaline behaviour of liquor ammonia is due to the presence of [NH + 4 ions/oh ions/h 3 O + ions] Ans. (i) Hydrogen (ii) neutral (iii) magnesium chloride (iv) NH 4 Cl (v) OH ions. Chemistry Class-X 8 Question Bank
28. Nitrogen gas is prepared in the laboratory by heating a mixture of ammonium chloride and sodium nitrite solutions. (i) Write a fully balanced equation for the above reaction. [1] (ii) Why is nitrogen not prepared by directly heating ammonium nitrite? [1] (iii) How is the drawback in (ii) overcome in reaction (i)? (iv) If instead of sodium nitrite, sodium hydroxide is added, name the gas evolved and write a fully balanced equation. [2] (v) How will you test the gas evolved in (iv)? [1] (vi) If instead of sodium nitrite, conc. sulphuric acid is added, name the gas evolved? Write fully balanced equation in support of your answer. [2] (vii) Give one test for the gas evolved in (vi). [1] Ans. (i) NH 4 Cl + NaNO 2 NaCl + NH 4 NO 2 (Sol) (sol) (sol) NH 4 NO 2 (sol) 2H 2 O + N 2 (g) (ii) It is because ammonium nitrite decomposes explosively when heated alone. (iii) At any time during the reaction, only a few molecules of ammonium nitrite are available. These molecules subsequently decompose to form nitrogen. Thus, the reaction becomes moderate and proceeds without explosion. (iv) The gas evolved will be ammonia. NH 4 Cl + NaOH NaCl + H 2 O + NH 3 (v) Bring a glass rod dipped in HCl, near the gas jar. Formation of dense white fumes confirms the presence of ammonia gas. (vi) The gas evolved is hydrogen chloride. 2NH 4 Cl + H 2 SO 4 (conc.) (NH 4 ) 2 SO 4 (vii) Introduce a glass rod dipped in ammonium hydroxide in the gas. The formation of dense white fumes confirms the presence of HCl gas. Chemistry Class-X 9 Question Bank
29. By stating experimental conditions and writing chemical equations, write how the nitrogen gas reacts with the following : [6] (i) Hydrogen gas (ii) Oxygen gas (iii) Magnesium powder. Ans. (i) One volume of nitrogen and three volumes of hydrogen at a pressure of 200 Atms. to 400 Atms. react in the presence of iron containing molybdenum at 450 C to form ammonia gas. Fe + MO at 450ºC N 2 + 3H 2 2NH 200 atms 3 (ii) On electric sparking, a mixture of nitrogen and oxygen reacts to form nitric oxide gas. Electric spark N 2 + O 2 2NO (iii) When burning magnesium powder is introduced in nitrogen, it continues burning and forms magnesium nitride. heat 3Mg + N 2 Mg 3 N 2 + Heat 30. Nitrogen can be prepared directly from air by removing oxygen and other impurities. Answer the following questions : (i) How are the acidic impurities such as carbon dioxide, sulphur dioxide, etc., removed from the air? (ii) How are the water vapours present in the air removed? [1] (iii) How is oxygen removed from the air? Support your answer by an equation. [2] (iv) How is nitrogen gas collected? [1] (v) The vapour density of nitrogen so collected is more than the vapour density of nitrogen collected by chemical reactions. Why is it so? [2] Ans. (i) The air is passed through caustic potash solution when the impurities such as carbon dioxide, sulphur dioxide, etc., react with caustic potash and hence are removed. (ii) The purified air is passed through conc. sulphuric acid. Here the sulphuric acid acts as drying agent and hence removes water vapour from the moist air. Chemistry Class-X 10 Question Bank
(iii) The oxygen is removed from the air by passing it slowly over heated copper gauze. heat 2Cu + O 2 2CuO (iv) The nitrogen gas is collected by the downward displacement of water. (v) The air contains about 1% of noble gases which do not undergo any chemical reaction. Thus, the nitrogen collected from air always contains noble gases, which in turn increase its vapour density. 31. Write fully balanced equations for the following reactions : (i) Aluminium nitride is treated with warm water. (ii) Ammonium sulphate crystals are warmed with sodium hydroxide. (iii) Ammonium chloride is warmed with slaked lime. (iv) Magnesium nitride is treated with warm water. Ans. (i) AlN + 3H 2 O Al (OH) 3 + NH 3 (g) (ii) (NH 4 ) 2 SO 4 + 2NaOH Na 2 SO 4 + 2H 2 O + 2NH 3 (g) (iii) 2NH 4 Cl + Ca(OH) 2 CaCl 2 + 2H 2 O + 2NH 3 (g) (iv) Mg 3 N 2 + 6H 2 O 3Mg (OH) 2 + 2NH 3 (g) 32. (i) Name two chemicals required for the laboratory preparation of ammonia gas. [1] (ii) Write a chemical equation when the chemicals named in (i) react. [1] (iii) Name the drying agent used for drying ammonia. (iv) Why cannot drying agents such as conc. H 2 SO 4, anhydrous calcium chloride and phosphorus pentoxide be used for drying ammonia? Support your answer with a chemical equation? [3] (v) How is dry ammonia gas collected in laboratory? (vi) How will you confirm that a gas jar is completely filled with ammonia gas? [1] (vii) Why should the apparatus for the collection of ammonia gas be perfectly dry? [1] Chemistry Class-X 11 Question Bank
Ans. (i) (1) Ammonium chloride (2) Calcium hydroxide. (ii) 2NH 4 Cl + Ca(OH) 2 CaCl 2 + 2H 2 O + 2NH 3 (g) (iii) Quicklime (CaO) is used as drying agent. (iv) It is because the named drying agents chemically react with ammonia to form ammonium salts. 2NH 3 + H 2 SO 4 (conc.) (NH 4 ) 2 SO 4 8NH 3 + CaCl 2 CaCl 2.8NH 3 6NH 3 + P 2 O 5 + 3H 2 O 2(NH 4 ) 3 PO 4 (v) Dry ammonia gas is collected by the downward displacement of air. (vi) Hold a glass rod dipped in HCl close to the mouth of the gas jar. The formation of dense white fumes confirms that the gas jar is completely filled. (vii) Ammonia is extremely soluble in water. Thus, if the apparatus is not dry, the ammonia gas will dissolve in moisture. 33. In the preparation of ammonia in industry, the raw materials are nitrogen and hydrogen. These are mixed together in the correct proportions needed to form ammonia. (i) Write the balanced equation for the manufacture of ammonia. [1] (ii) How much hydrogen would there be in 400 litres of gaseous mixture required for the manufacture of ammonia? [2] (iii) 1. If all nitrogen and hydrogen used were converted into ammonia, find the volume of ammonia formed. [1] 2. How would the volume of ammonia formed compare with the volume of original mixture? [1] (iv) The formation of ammonia from its elements is an exothermic reaction. What is meant by exothermic? (v) Ammonia produced is removed from unchanged gases in one of the two possible ways. Mention the two ways. [2] Chemistry Class-X 12 Question Bank
Fe + Mo at 450ºC Ans. (i) N 2 + 3H 2 2NH 200 atms 900 atms 3 + heat (ii) 300 litres. (iii) (1) 200 litres. (2) The volume of ammonia is half of the volume of the mixture of gases. (iv) It means, reaction proceeds with the evolution of heat. (v) (1) The mixture of gases is suddenly cooled and then allowed to expand. Thus, ammonia liquefies and separates. (2) The mixture is passed through water, when ammonia dissolves in water. Chemistry Class-X 13 Question Bank