Reaction Engineering

Questions & Answers

Section B: Problems in Chemical Kinetics


The reaction A→ B occurs in a continuously stirred batch reactor. The following data in the table below was collected by an engineer. What is the reaction time needed to achieve 10%, 50%, and 75% conversions? Hint: You will have to determine the reaction order in A first. The order of the reaction is a positive integer.


Build a spreadsheet (or computer code) that can be used to solve an ideal vapor liquid


b. An equimolar mixture of: 40% n-butane, 10% n-hexane, 10% n-heptane, 20% benzene, and 20% toluene are fed to the flash separator at 35 °C and 100 kPa: i. What are the dew and bubble pressures? (A: 100 kPA, 20 kPa) ii. What fraction of the mixture is vapor and what fraction of the vapor is benzene? (A: 20% vapor, 5% benzene)


C. For the mixture in (b), at what pressure is the mixture only 5% vapor? What is the mole fraction of n-butane at this condition? (A: 100 kPa, 0.9 butane)


The second-order reversible reaction 2A B takes place in an isothermal, isobaric flow reactor. Pure A is fed at a concentration of 5 mol/L. The equilibrium conversion is measured to be 60%. a. If the reaction occurs in the liquid phase, what is the equilibrium constant, K? b. If the reaction occurs in the gas phase, what is the equilibrium constant, K? c. If the reaction occurs in the gas phase and an inert is added with the concentration of 5 mol/L, what is the equilibrium constant, K?


Section C: Problems in Basic Reactor Engineering


Section B: Problems in Chemical Kinetics


Question A2: The ground state oxygen atom Write down a kinetic equation (net rate law) for the concentration change of ground-state oxygen atoms with time, where t represents time, neglecting equation (A.2). Integrate your rate law, to afford an analytical expression showing the actual variation of the ground-state oxygen atom concentration with time, under conditions of constant irradiation, and that all species M are present in excess. Make sure you identify appropriate boundary conditions. Use the steady-state approximation and your kinetic equation to determine the steady-state concentration of ground-state oxygen atoms. Then, identify whether the steady-state hypothesis is a suitable approximation to apply to ground-state oxygen atoms in atmospheric modelling. Comment on any similarities or differences you have found in the application of the steady-state approximation for the reactive intermediates (O and O) considered in Questions A1 and A2.


Question A1: The excited oxygen atom Write down a kinetic equation (net rate law) for the concentration change of excited oxygen atoms with time, lo where t represents time. de (2 marks) Integrate your rate law, to afford an analytical expression showing the actual variation of the excited oxygen atom concentration with time, given that no o* exists prior to t = 0. HINT: you may find that making assumptions that land [M] are independent of time to be helpful! (6 marks) Use the steady-state approximation and your kinetic equation to determine the steady-state concentration of excited oxygen atoms., and identify under what conditions the actual variation of the excited oxygen atom concentration corresponds to the steady-state variation. (2 marks) Then, estimate the minimum illumination time required for the non-steady state and steady-state concentrations to be identical to within 19. (4 marks) Comment on whether the steady-state hypothesis is a good approximation for the atmospheric behaviour of excited oxygen atoms where the solar intensity changes over periods of hours.


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