5-8. For irreversible reactions the maximum conversion is unity, regardless of temperature level. Since the rate normally increases with temperature, the maximum conversion is obtained in a given reactor if the temperature is at its highest permissible level at every location in the reactor. The permissible temperature limit is determined by the possibility of undesirable side reactions and strength or corrosion resistance of construction materials. For endothermic reversible reactions both rate and maximum conversion increase with temperature. Here again the highest permissible temperature gives the maximum conversion. For reversible exothermic reactions increasing the temperature reduces the maximum (equilibrium) conversion but increases the forward rate. To obtain the maximum conversion a high temperature is needed at low conversions (where the reverse reaction is unimportant) and a lower temperature at higher conversions. Consider a reversible first-order reaction AB for which, at 298K, F298=2500cal/g mole H298=20,000cal/gmole The reaction mixture is an ideal liquid solution (constant density) at all temperatures. (a) Assuming that H is constant, plot a curve of the equilibrium conversion vs temperature from 0 to 100C. (b) If the forward-rate constant is k=5108e12,500/RgTmin1 determine the conversion in the effluent from an isothermal tubular-flow reactor for which the volumetric feed rate is 100 liters/min and the reactor volume is 1,500 liters. Calculate the conversion for a series of temperatures from 0 to 100C and plot the results on the figure prepared for part (a).(c) Suppose that the maximum permissible temperature is 100C and the concentration of A in the feed stream is 2g moles/liter (the feed contains no B ). Determine the maximum conversion obtainable in the reactor of part (b) if the temperature can be varied along the length of the reactor. First prepare curves of net rate vs temperature at constant conversion for several conversion levels. Note that each curve will show an increase in rate with temperature increase at low temperatures. Then as the temperature corresponding to equilibrium for the fixed conversion is approached the curve will go through a maximum,-and it will finally fall to zero rate when this temperature is reached. The maximum conversion in the reactor effluent will be obtained when the net rate is a maximum at every position (or conversion) in the reactor. Hence the locus of the maxima in the curves for net rate vs temperature will determine the optimum temperature profile. Plot this profile, first as temperature vs conversion and then as temnerature vs VHO