Ammonia is a colorless gas with a sharp, irritating odor. It is extremely soluble in water and is lighter than air. AMMONIA (NH3)

Physical Properties of NH3Ammonia, NH3Atomic mass:17.0306 g/molmelting point-77.7 oCboiling point-33.3 oC

History Ammonia was first isolated by Priestley in 1774 with the aid of a pneumatic trough filled with mercury instead of water.

Natural Abundance Ammonia is produced by the anaerobic decay of organic material. Ammonia was the first complex molecule to be identified in interstellar space and solid NH3 makes up the rings on Saturn.

Industrial Production Prior to the 20th century, ammonia was made by destructive distillation of animal parts such as hoofs, horns, etc. The common name for ammonia was Spirits of Hartshorn. In 1913, Haber worked out a synthetic route to catalytically produce ammonia from the elements at high pressure and temperature. The Haber process is still used today.

Ammonia is made by the Haber process from nitrogen and hydrogen:N2 (g) + 3H2 (g) 2NH3 (g) + Heat H = -92 kJ mol-1The reaction is exothermic, and involves a decrease in the number of moles of gas. Based on Le Chateliars Principle, the reaction is favored by low temperature and high pressure. At low temperature, the rate attained of equilibrium is slow. Hence a compromised temperature of 450 - 500 C is adopted (to increase the rate of reaction)

Haber-Bosch Process* Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling

Uses of AmmoniaFertilserproduction of:ammonium sulfate, (NH4)2SO4ammonium phosphate, (NH4)3PO4ammonium nitrate, NH4NO3urea, (NH2)2CO,also used in the production of barbiturates (sedatives), is made by the reaction of ammonia with carbon dioxide

Fibres and Plasticsnylon, -[(CH2)4-CO-NH-(CH2)6-NH-CO]-,and other polyamides

Refrigerationused for making ice, large scale refrigeration plants, air-conditioning units in buildings and plants

Pharmaceuticalsused in the manufacture of drugs such as sulfonamide which inhibit the growth and multiplication of bacteria that require p-aminobenzoic acid (PABA) for the biosynthesis of folic acids, anti-malarials and vitamins such as the B vitamins nicotinamide (niacinamide) and thiamine.

Gas Density of NH3 The density of NH3 is 0.6826 g/L at 25 oC and 1 atm. This is about half that of airs, thus it tends to rise in a still room.

Gas Solubility of NH3 Ammonia is extremely soluble in water. As much as 89.9 g dissolve per L at 0 oC. This means that 1 mL of water will dissolve 1183 mL ammonia! At 100 oC, the solubility drops to 7.4 g ammonia /100 mL H2O (113 volumes NH3 per 1 volume water.)

LABORATORY PREPARATION OF AMMONIAApparatus Round bottomed flask, clump,Bunsen burner, delivery tube, trough, curdboard, wire gauze, lime water.Chemicals Calcium hydroxide,Ammoniumchloride, Calcium oxide.ProcedureAmmonia is prepared by heating a mixture of calcium hydroxide and ammonium chloride.

Ca(OH)2(s) + 2NH4Cl(s) CaCl2(s) + 2H2O(i) + 2NH3(g)

The tube in which ammonia is generated is fixed in a slanting position to prevent thewater formed from running back and crack the whole tube.

Concentrated sulphuric acid and anhydrous calcium chloride are not used to dryammonia because they react with it. Ammonia is collected by upward delivery as it islighter than air.

HABER PROCESS (INDUSTRIAL PREPARATION)

Apparatus Compressing chamber,catalytic chamber,cooling chamber,delivery tube.Chemicals Finelydivided iron, AlminiumOxide, Water, Hydrogen,Nitrogen.

Procedure:

It is manufactured by reacting Nitrogen and hydrogen inthe presence of finely divided iron as a catalyst attemperatures 350C - 400C at a pressure of about 350atmospheres.

N2(g) + 3H2(g) 2NH3(g)

Alminium Oxide is added to the catalyst to improve itsperformance. It makes it more porous and this provides ahigh surface area to the reaction.The reaction isreversible hence it is not possible to convert allthe reactants into ammonia. To separate ammonia fromthe mixture is cooled, only ammonia liquidfies and it isseparated. The uncombined Nitrogen and hydrogen arerecycled.Another way of separation is to pass the mixtureinto water. Only ammonia dissolves.

FACTORS AFFECTING THE REACTION (PROCESS)Pressure

High pressure causes a better yield of ammonia because it favours the formation of thesmaller products. It also increases the speed of reaction because the reacting moleculescollide more often.

Temperature

At low temperatures the yield at equilibrium of Ammonia is higher but the reaction is slow.At high temperatures the yield of ammonia is low but the reaction is fast, a temperature ofabout 500C is used. The yield is good but the reaction is still too slow. A catalyst istherefore necessary to speed up the reaction.

Catalyst

A catalyst speeds the reaction but does not affect the equilibrium. The catalyst should befinely divided because reaction occurs only at the surface

Uses of ammoniaIt is used in the manufacture of fertilizers e.g. Ammonium sulphate.It is used in softening water.It is used in making nitric acid.It is used in making plastics.Ammonium chloride is used in dry cells.It is used in making explosives.

Test for AmmoniaIt is the only common alkaline gas known. It changes the dump / wet litmus paper blue.

Ammonia forms dense fumes of ammonium chloride when brought into contact with fumes of hydrogen chloride from concentrated hydrochloric acid.