CBEMS 45A Final - p. 1 1. [5 pts.] Short Answers The Antoine equation relates ______ and _______ . For atomic balances, the generation and consumption terms can always be neglected. _____ (T/F) A flask contains 4 components in 2 phases. There are ________ degrees of freedom. The number of degrees of freedom is the maximum number of __________ variables that can be specified. Give the equations for: Pr = ________, Vr = _________ . For solid-liquid equilibrium, the liquid phase must be ___________ with the solid. For recycle reactors, single pass conversion is _________ than overall conversion. The pressure at the top of a tank of liquid is P0. The pressure at the bottom is P = ___________ . 2. [7 pts.] Sketch a Txy diagram. Show the three regions: vapor, liquid, and VLE. For a mole fraction of 0.5, show the dewpoint, the bubblepoint, and an intermediate VLE point. For the intermediate point, show the vapor and liquid compositions. 3. [4 pts.] A process is represented by the flowchart to the right. No reactions occur. You want to determine the concentrations of all streams. What is the maximum number of independent balances that can be written? Explain carefully.

A A, B

C

^

CBEMS 45A Final - p. 2 4. [9 pts.] Chemical Reaction Ethylene is oxidized to ethylene oxide by the reaction:

2C2H4 +O2 2C2H4O For the above flowchart, answer the following questions: (a) If n1=3n2, which reactant is limiting? (b) If x moles of O2 react, how many moles of C2H4O are formed? (c) Write the expression for fractional conversion of ethylene (

fC2H4 = ........)? (d) Write expressions for n3, n4, and n5 using extent of reaction. (e) Write the atomic balances for C, H, and O.

n1 C2H4 n2 O2

n3 C2H4 n4 O2 n5 C2H4O

CBEMS 45A Final - p. 3 5. [20 pts.] Dryer Wet leather enters a continuous tunnel dryer with a moisture content of 61 wt%. The leather leaves the dryer at a rate of 485 lbm/h with a moisture content of 6.0 wt%. Dry air (0% relative humidity) at 140oF and 1.0 atm enters the dryer. The wet air stream leaving the dryer is at 130.oF and 1.0 atm and has a relative humidity of 50.%. (a) Draw the flowchart for the process. Include the given values. (b) What is the mass flow rate of the wet leather entering the dryer? (c) What is the volumetric flowrate (ft3/h) of the inlet air stream?

CBEMS 45A Final - p. 4 6. [20 pts.] Dry air (0% relative humidity) is bubbled through 40.0 liters of water at a rate of 25.0 liters/min in a room at 25.0oC and 1.00 atm. The exit gas is saturated with water. (a) What is the mole fraction of water in the exit stream? (b) What is the total molar flowrate leaving the tank? (c) How long will it take for all of the water to be carried off?

CBEMS 45A Final - p. 5 7. [35 pts.] Combustion Fuel oil (C18H36) is burned at a rate of 2000 kg/h with 50% excess air. The conversion of the fuel is 100%. The combustion products are sent to a dryer to remove all of the water (a negligible amount of water remains in the dry gas). Analysis of the dry gas shows a ratio of CO2 to CO of 2 (on a molar basis), a temperature of 135oC, and a pressure of 18 psia. (a) What is the molar flowrate of O2 in? (b) What is the composition of the dry flue gas (mol %) leaving the dryer? (c) What is the volumetric flowrate (m3/h) of the dry gas stream?