课程名称︰质能平衡甲 课程性质︰系定必修 课程教师︰林祥泰 开课学院：工学院 开课系所︰化工系 考试日期（年月日）︰97.03.25 考试时限（分钟）：110分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : Note:Data needed for the calculations are provided in the back of this paper. Credit for each problem is given in the square brackets []. Be sure to write down how you reach the answers. No credit will be given to answers without providing sufficient explanation. 1.The health limit of contaminant carbon tetrachloride(CCl4) in drinking water is 5 ppb. What is this value in terms of mass fraction, mole fraction, molarity , and molality?[10pts] 2.In the degrees-of-freedom analysis, what are the sources of relations that can be used to solving the unknowns in a non-reactive process? Briefly explain your answer.[10pts] 3.Shown below is a flowchart of a process in which acetic acid(A) is extracted from a mixture of acetic acid and water(W) into 1-hexanol(H), a liquid immiscible with water. . . mH(g C6H13OH/min) mE(g/min) ────────→╭┬─┬╮─────────────→ . ││ ││. 0.096g CH3COOH/g mF(g/min) ││ ││mR(g/min) 0.904g C6H13OH/g ────────→╰┴─┴╯────────→ 0.200g CH3COOH/g 0.005g CH3COOH/g 0.800g H2O/g 0.995g H2O/g a)What is the maximum number of independent material balances that can be written for this process?[5pts] b)Suppose we wish to recover acetic acid from the extract(i.e.,the mE stream) at a rate of 100g/min. Determine the mass flow rates mH,mF,mE, and mR.[10pts] 4.A material containing 75wt% water and 25wt% solid is fed to a granulator at a rate of 4000kg/hr. The feed is premixed in the granulator with recycled product from a dryer which follows the granulator(to reduce the water concentration of the overall material in the granulator to 50wt% water, 50wt% solid). The produce that leaves the dryer is 16.7wt% water. In the dryer, air is passed over the solid being dried. The air entering the dryer contains 3wt% water, and the air leaving the dryer contains 6wt% water. air ────┐ ↓ feed ┌─────┐ ┌───┐ air ────→│granulator├────→│dryer ├────→ │ │ │ ├──┬─→ └─────┘ └───┘ │ product ↑ │ └───────────────┘ a)Draw and complete the flowchart of this process, and label all the unknowns. [10pts] b)Circle the subsystems that can be used for analyzing this problem.[5pts] c)Perform degrees-of-freedom analysis on all the subsystems.[10pts] d)determine the mass flow rate of air entering the dryer.[10pts] 5.An inclined manometer(shown below) is used to measure small pressure difference ┌─────1───2─────┐ └────┐┌──┐┌────┘ ＼╱╱﹍﹍╱╱ L ╱╱﹉ ◢◤﹉﹉↑ ＼╱╱﹍﹍◢◤θ ↓h ◢◤﹉ ◢◤﹉﹉﹉﹉ ████◤ a)Derive a formula for h(liquid-level difference) in terms of L(reading) and θ (angle of inclination)?[5pts] b)Suppose the manometer fluid is mercury(SG=13.6), the process fluid is water, the inclination of the manometer is θ=20.0°, and a reading of L=10.0cm is obtained. What is the pressure difference between the two points 1 and 2?[5pts] 6.The values of diffusivity of methane in zeolite were measured to be 1.9×10^-11 and 20.1×10^-11 m^2/s at 200.K and 300.K, respectively. Suppose the temperature dependence of diffusivity follows the Arrhenius equation: D=D0exp(-E/RT) where R is gas constant 8.314J/mol K. a)Determine the value and unit of D0 and E.[10pts] b)Derive the formula for D in AES units(e.g.D in ft^2/s, T in °R).[10pts] --

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