nitrogenfromthe air400-450°C200atmnitrogen and hycrogeniron catalyst1:3byvolumeunreactedgaseshydrogenrecydedfromnatural gasgasesaremoledandammoniatumsto liquidliquid ammonia△AH= -92 kJ mol-111
11 △H= -92 kJ mol - 1
400-450° Cis a compromise temperatureproducing a reasonably high proportion ofammonia in the equilibrium mixture (even if it isonly 15%), but in a very short time.2oo atmospheres is a compromise pressurechosen on economic grounds. If the pressureused is too high, the cost of generating it exceedsthe price you can get for the extraammoniaproduced.SeparatingtheammoniaWhen the gases leave the reactor they are hotand at a very high pressure. Ammonia is easilyliquefied under pressure as long as itisn't too hot.and so the temperature of the mixture is loweredenough for the ammonia to turn to a liquid. Thenitrogen and hydrogen remain as gases evenunder these high pressures, and can be recycled.12
12 • 400 - 450°C is a compromise temperature producing a reasonably high proportion of ammonia in the equilibrium mixture (even if it is only 15%), but in a very short time. • 200 atmospheres is a compromise pressure chosen on economic grounds. If the pressure used is too high, the cost of generating it exceeds the price you can get for the extra ammonia produced. • Separating the ammonia When the gases leave the reactor they are hot and at a very high pressure. Ammonia is easily liquefied under pressure as long as it isn't too hot, and so the temperature of the mixture is lowered enough for the ammonia to turn to a liquid. The nitrogen and hydrogen remain as gases even under these high pressures, and can be recycled
Nitrogenchemistry:keyfactsNitricacidproductionAmmonia made in the Haber process is oxidized to makenitric acid. Ammonia is mixed with air and passed over acatalyst of platinum. Further reaction with air and thenwater yields nitric acidPt4NH(g)+502(g)+ 4NO(g)+6H,O(g)850C2NO(g)+O2(g) → 2NO2(g)4NO2(g)+O2(g)+2H,O(1) → 4HNO,(I)The main use of nitric acid is in explosive manufacture13
13 Nitrogen chemistry: key facts Nitric acid production Ammonia made in the Haber process is oxidized to make nitric acid. Ammonia is mixed with air and passed over a catalyst of platinum. Further reaction with air and then water yields nitric acid. Pt 4NH3 (g)+5O2 (g) 4NO(g)+6H2O(g) 850oC 2NO(g)+O2 (g) → 2NO2 (g) 4NO2 (g)+O2 (g)+2H2O(l) → 4HNO3 (l) The main use of nitric acid is in explosive manufacture
Nitrogen chemistry: key ideasNitrogen is an elementNitrogen is a covalently bonded, molecular gas. It exists as diatomicmolecules. The triple bond between the nitrogen atoms is very strong sonitrogen is very unreactive.Phosphorus in the same group exists as P4 molecules (white phosphorus)with single bonds between the atoms. These bonds are weak and there isbond strain, because the bond angles are only 6oo. This makesphosphorus very reactive.944kJmo-1XOGNNDXxO172kJmof-1PObondanglesof60C14
14 Nitrogen chemistry: key ideas Nitrogen is an element Nitrogen is a covalently bonded, molecular gas. It exists as diatomic molecules. The triple bond between the nitrogen atoms is very strong so nitrogen is very unreactive. Phosphorus in the same group exists as P4 molecules (white phosphorus) with single bonds between the atoms. These bonds are weak and there is bond strain, because the bond angles are only 60o . This makes phosphorus very reactive
Allotropes of phosphorusWhite phosphorus is a white, waxy transparent solidThis allotrope is thermodynamically unstable at normalcondition and will gradually change to red phosphorus.whiteRed phosphorus is formed by heatingphosphorus to 250° C (482° F) or by exposing whitephosphorus to sunlight.Red phosphorus is not poisonous and is not asdangerous as white phosphorus, although frictional heating isenough to change it back to white phosphorus. Redphosphorus is used in safety matches, fireworks, smokebombs and pesticides.15
15 Allotropes of phosphorus White phosphorus is a white, waxy transparent solid. This allotrope is thermodynamically unstable at normal condition and will gradually change to red phosphorus. Red phosphorus is formed by heating white phosphorus to 250°C (482°F) or by exposing white phosphorus to sunlight. Red phosphorus is not poisonous and is not as dangerous as white phosphorus, although frictional heating is enough to change it back to white phosphorus. Red phosphorus is used in safety matches, fireworks, smoke bombs and pesticides