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Urea (H2NCONH2) is used extensively as a nitrogen source in fertilizers. It is produced commercially from the reaction of ammonia and carbon dioxide. 2 NH3(g) + CO2(g) --> H2NCONH2(s) + H2O(g) Ammonia gas at 223°C and 90. atm flows into a reactor at a rate of 650. L/min. Carbon dioxide at 223°C and 45 atm flows into the reactor at a rate of 600. L/min. What mass of urea is produced per minute by this reaction assuming 100% yield?

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1. The number of moles of NH3 that is flowing into the reactor per minute is (using PV=nRT): (90 atm) (650 L/min) / (0.082 L-atm/K-mol) (223 + 273.15 K) = 1,437.9 mol/min NH3. The number of moles of CO2 that is flowing into the reactor per minute is: (45 atm) (600 L/min) / (0.082 L-atm/K-mol) (223 + 273.15 K) = 663.6 mol/min CO2. We see by the balanced reaction equation that NH3 and CO2 react in a 2:1 molar ratio. Since 1,437.9 / 663.6 = 2.17, then we see that CO2 is the limiting reagent, and therefore urea will be produced at the same molar rate as carbon dioxide is being added. The excess NH3 will pass out of the reactor unreacted. The molecular mass of urea is 60.1 g/mole, so: (663.6 mol/min) (60.1 g/mole) = 39,885 g/min.