CHE499 TRANSPORT MODELING Spring 2008
Problem set #2
(1)(p. 14.1[1]) Assuming air to be composed exclusively of O2 and N2, with their partial pressures in the ratio 0.21:0.79, what are their mass fractions?
(2) (p. 14.21) A mixture of CO2 and N2 is in a container at 25oC, with each species having a partial pressure of 1 bar. Calculate the molar concentration, the mass density, the mole fraction, and the mass fraction of each species.
(3) (p. 14.41) Consider the interface between atmospheric air and a body of water, both at 17oC.
(a) What are the mole and mass fractions of water at the air side of the interface? At the water side of the interface?
(b) What are the mole and mass fractions of oxygen at the air side of the interface? At the water side of the interface? The atmospheric air may be assumed to contain 20.5% oxygen by volume.
(4) The population of mosquitoes in a certain area increases at a rate proportional to the current population and, in the absence of other factors, the population doubles each week. There are 200,000 mosquitoes in the area initially, and predators eat 20,000 mosquitoes/day. Determine the population of mosquitoes in the area as a function of time t in week. Determine the population when t = 4 week.
(5)[2] Consider the following first order liquid phase reaction
A B
The volumetric flow rate is 10 liter/min and the rate constant k = 0.23 min-1. Calculate both the CSTR and PFR reactor volumes to reduce the exit concentration to 10% of the entering value.
(6)2Consider the following first order liquid phase reaction
A B
The rate constant, k, is equal to 0.23 min-1. Calculate the time to reduce the number of moles of A to 1% of its initial value in a constant volume batch reactor.
(7)2 Consider the following first order liquid phase reaction
A B
Calculate both the CSTR and PFR reactor volumes to reduce the exit concentration to 1% of the entering value. The entering molar flow rate is 5 mol/hr and the entering volumetric flow rate is 10 L/hr. The following reaction rate is assumed:
(a) rA = kwith k = 0.05 mol/Lhr
(b) rA = kCAwith k = 0.0001 s-1
(c) rA = kCA2with k = 3 L/molhr
(8)2 The gas phase reaction
A B + C
is carried out isothermally in a 20 L constant-volume batch reactor. Twenty moles of pure A is initially placed in the reactor. The reactor is well mixed.
(a)If the reaction is first order:
rA = kCAwith k = 0.865 min-1
calculate the time necessary to reduce the number of moles of A in the reactor to 0.2 mol.
(b)If the reaction is second order:
rA = kCA2with k = 2 L/molmin
calculate the time necessary to consume 19 moles of A.
(c) If the temperature is 127oC, what is the initial total pressure? What is the final total pressure assuming the reaction goes to completion?
[1] Incropera, Fundamentals of Heat and Mass Transfer, Wiley, 2002
[2] Fogler, H. S., Elements of Chemical Reaction Engineering, Prentice Hall, 1999