INDUSTRIAL APPLICATIONS Haber process And Contact process

Haber process Manufacture of ammonia N 2 (g) +3H 2 (g)  2NH 3 (g),  H= -92kJmol -1 ( exothermic ) a.Uses of ammonia : manufacture fertilisers, dyes and explosives b.LCP suggest that high pressure and low temperature will shift equilibrium to the right and produce more ammonia

c. However,other economic factors (time and cost factors) must also be considered such as: i) Low temperature not used – rate is slow Note : high temperature also not used because Equilibrium shifts left, lower yield Therefore use a moderate temperature

ii) pressure not too high Reason : High pressure incurs higher cost of maintenance and also more expensive to build

d. Optimum conditions : 450 – C 100 – 250 atm Catalyst Fe Note : % yield of NH 3 = less than 20 % Pressure used reasonably high due to : Forward reaction favored, more NH 3 Higher collision frequency, faster reaction

Contact process Manufacture of sulphuric acid (1) S(g) + O 2 (g)  SO 2 (g) (2) 2SO 2 (g) + O 2 (g)  2SO 3 (g)  H= -192kJ mol -1 ( exothermic ) (3) SO 3 (g) + H 2 SO 4 (l)  H 2 S 2 O 7 (l) oleum H 2 S 2 O 7 (l) + H 2 O (l)  2H 2 SO 4 (aq)

a. LCP suggest that high yield of SO 3 (equilibrium shifts right) is favored by high pressure and low temperature b. Optimum conditions : 400 – C 1 – 2 atm ( % yield = 95 % hence high pressure not used ) Catalyst (vanadium pentoxide,V 2 O 5 )

High yield achieved under the following conditions: (1) Air used to burn sulphur must be clean Reason : Catalyst easily poisoned/damaged (2) Catalyst needs to be cooled Reason : Exothermic rxn hence catalyst gets hot Or low temp favors forward reaction