
	Trending ▼ ICSE CBSE 10th ISC CBSE 12th CTET GATE UGC NET Vestibulares ResFinder

ammonia

4 pages, 1 questions, 1 questions with responses, 1 total responses,

$ω@T!*
Ashoka Universal School (AUS), Nashik
11th-12th

+Fave Message

Profile Timeline Uploads

Home > swati22 >

Formatting page ...

Ammonia 1. Ammonia gas can be prepared by the following chemical methods : (i) By warming ammonium salts with alkalis : heat NaCl + H2O + NH3 NH4Cl + NaOH (ii) By the action of water on metallic nitrides : AlN + 3H2O Al(OH)3 + NH3 (iii) From elements : Fe + Mo at 450 C 2NH3 + N2 + 3H2 200 Atms 9000 Atms 2. In the laboratory, ammonia gas is prepared by heating a mixture of ammonium chloride and calcium hydroxide. 2NH4Cl + Ca(OH)2 CaCl2 + 2NH3 + 2H2O Ammonia is dried by passing through quicklime and collected by the downward displacement of air. 3. Ammonia gas cannot be dried over (i) conc. sulphuric acid (ii) phosphorus pentoxide (iii) anhydrous calcium chloride as they react with it to form ammonium salts. 4. Haber s process : One volume of dry nitrogen and three volumes of dry hydrogen are compressed to 200 atms 900 atms. The mixture is passed over electrically heated catalyst iron, which contains molybdenum as promoter. An exothermic and reversible reaction takes place with the formation of ammonia gas. Fe + Mo at 450 C 2NH3 + N2 + 3H2 200 Atms 9000 Atms The yield is about 60%. In order to carry the reaction in forward direction, the products are suddenly cooled, so that ammonia liquefies and separates out. The unreacted mixture of gases is recompressed and again passed over catalyst. 1 Key Points 5. Physical properties of ammonia gas : (i) It is a colourless gas which fumes strongly in air. (ii) It has a sharp burning smell which brings tears to the eyes. (iii) It is highly soluble in water. One volume of water can dissolve 1300 volumes of gas. (iv) It is lighter than the air. Its V. D. is 8.5, compared to air, whose V.D. is 14.4. (v) It is non-poisonous in nature. However, being basic in character, it damages the respiratory system. 6. Chemical properties of ammonia gas : 1. It dissolves in water to form ammonium hydroxide. Thus, it turns moist red litmus paper blue. NH3 + H2O NH4OH 2. It reacts with acids to form ammonium salt. 2NH3 + H2SO4 (NH4)2SO4 3. It burns in the atmosphere of oxygen to form nitrogen and steam. 4NH3 + 3O2 2N2 + 6H2O 4. When the mixture of ammonia and oxygen is passed over heated platinum at 900 C, it forms a mixture of nitric oxide and steam. Pt 900 C 4NH3 + 5O2 4NO + 6H2O 5. When ammonia reacts with excess of chlorine, it forms nitrogen trichloride and HCl. NH3 + 3Cl2 NCl3 + 3HCl 6. When ammonia reacts with limited amount of chlorine, it forms ammonium chloride and nitrogen. 8NH3 + 3Cl2 6NH4Cl + N2 7. It reacts with hot sodium and potassium metals to form their amides. 2Na + 2NH3 2NaNH2 + H2 8. It reduces black copper (II) oxide to copper metal. Similarly, it reduces lead oxide to lead metal. 3CuO + 2NH3 3Cu + N2 + 3H2O 2 Key Points 7. Chemical properties of ammonium hydroxide : In addition to the properties described above, ammonium hydroxide has the following properties : (i) It reacts with soluble salts of metals (except salts of sodium and potassium) to form their insoluble hydroxides. CuSO4 + 2NH4OH Cu(OH)2 + (NH4)2SO4 FeCl3 + 3NH4OH Fe(OH)3 + 3NH4Cl (ii) When ammonium hydroxide solution is added to copper sulphate solution, it first forms bluish white ppt. of Cu(OH)2, which dissolves in excess of ammonia to form complex cupro ammonium ion, which has a deep blue colouration. CuSO4 + 2NH4OH Cu(OH)2 + (NH4)2SO4 Cu(OH)2 + (NH4)2SO4 + 2NH4OH [Cu(NH3)4] SO4 + 4H2O (iii) It forms white ppt. with silver nitrate solution. The precipitate dissolves in excess of NH4OH to form soluble argento ammonium ions. AgNO3 + NH4OH NH4NO3 + AgOH AgOH + 2NH4OH [Ag(NH3)2]OH + 2H2O 8. Uses of ammonia and ammonium hydroxide : (i) It is used in the manufacture of fertilisers such as urea, ammonium sulphate, etc. (ii) It is used in the manufacture of nitric acid. (iii) It is used in the manufacture of salts like ammonium chloride, which is used in medicines. (iv) NH4Cl is also used in dry cell industry and in the tin industry. (v) It is used in the manufacture of washing soda and baking soda. (vi) It is used as a refrigerant in ammonia ice plants. (vii) It dissolves grease and is used as a cleansing agent for removing grease spots. (viii) It is used as an important laboratory reagent. 3 Key Points 9. Tests of ammonia : 1. It has a characteristic burning smell which brings tears to eyes. 2. It turns red litmus paper blue, turmeric paper brown and phenolphthalein solution pink. 3. It forms dense white fumes with hydrochloric acid gas. 4. It turns Nessler s solution brown. 5. It forms bluish white ppt. with copper sulphate solution. The precipitate dissolves in excess of ammonia to form deep blue colouration. 4 Key Points

Formatting page ...

Top Contributors
to this ResPaper
(answers/comments)

$ω@T!*
(1)

Formatting page ...

swati22 chat

Horizontal lines at:
Guest Horizontal lines at:
AutoRM Data:
Box geometries: