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engineering
chemical engineering
Questions and Answers of
Chemical Engineering
In concentration polarization if bulk and surface concentration of the solute is 5 and 2 mM, respectively, then estimate the flux through the membrane if mass transfer coefficient is 0.01 mol/cm2/min.
Estimate the number of stages for a countercurrent extractor train, if the EF = 0.5 and the extraction efficiency is (a) 90% and (b) 99%.
Derive the equation for Langmuir adsorption isotherm.
A solution of sucrose in water is concentrated by RO. It is found that, with a differential applied pressure of 6000 kPa, the rate of movement of the water molecules through the membrane is 25 kg
If the sucrose concentration is 20% what will be the flow rate at the higher pressure in the previous problem.
It is desired to increase the protein concentration in whey by a factor of 10 by the use of membrane filtration to give an enriched fraction to produce a 50% protein whey powder. The whey initially
Assume that the membrane rejection of the protein is over 99% and calculate the membrane rejection of the non-protein constituents in the previous problem.
The retention time of a protein in a column is 9.0 min, and that the standard deviation is 0.4 min. Estimate the equivalent number of equilibrium stages in this column.
A protein is present as 70% and rest impurity in a mixture. Laboratory data suggest a retention time of 9.0 hr. with a standard deviation of 0.6 hr. for the former compound and 8.hr. with a standard
State the stationary and moving phases in each type of chromatography below:a) thin layerb) columnc) gas
Two proteins A and B are chromatographed through a bed. The total volume of the bed is 100 L and void fraction is 0.30. The equilibrium constants K are 10.0 and 12. 0 for A and B, respectively.
What is the resolution of two Gaussian peaks of identical width (3.27 s) and height eluting at 67.3 s and 74. 9 s, respectively?
About 15 g of a protein mixture is flowing through a column at a velocity of 30 cm/hr., the peak in concentration exists the column in 90 min and the standard deviation of this peak is given as 10
Calculate the number of theoretical plates when the time at which peak appears is 10 min and the width of the base is 1. 2 min.
How many stages are required to recovery 90% of a protein if the flow rate is 10 L/min, porosity is 0.33, partition coefficient is 54, bed volume is 100 L.
Derive the mathematical equation relating the width at the base and width at half height in a chromatogram
Estimate the Resolution between two peaks A and B if the time at which peak maximum occurs are 8 and 12 min, respectively. The widths at the base are 3 and 4 min, respectively.
What is the heat required to evaporate 1000 kgs of water at 100°C?
The length of a crystal increased from 0.1 mm to 0.15 mm in 10 min. What is the growth rate if the crystal growth follows McCabe’s law?
If a copper cylinder of length 5 cm and diameter of 2 cm is heated from one end at 100°C, while the other end is at 30°C, what is the rate of heat transfer. If the material is made of iron what
Air at 70°C is heating solids at 30°C by convection. The area of heat transfer is 10 cm2 and the heat transfer coefficient is 2 kJ/cm2/K/s. What is the rate of heat transfer? What are the
For fluid similar to water, if the velocity is doubled what will be the increase in the heat transfer coefficient? If the viscosity is doubled what will be the change in the heat transfer coefficient?
In radiation heat transfer, if the temperature of the black body increases from 250 to 260°C, what will be the increase in the radiation energy?
What are the different techniques that can be adopted to double the rate of drying in conduction?
In spray drying if the particle size is reduced from 120 microns to 100 microns, what will be the increase in heat transfer rate?
If the heat transfer coefficient of the hot and the cold fluid sides are neglected, what will be the change in the overall heat transfer coefficient if aluminum is used instead of stainless steel?
If 120 kcals/sec of heat is applied to water for evaporation, what will be the rate of evaporation of water?
How long it will take to reduce the pressure of a 100 L tank from 1 Kg/cm2 (a) to 0.2 Kg/cm2 (a), if the pump capacity is 500 L/min. assume 10% leakage.
In a rising film evaporator, if the heat transfer coefficient is proportional V0.6, where V is the rising vapor velocity. If the throughput through the reactor has to be increased by 25%, how many
What will be change in the heat transfer coefficient in problem 2 after the modification?Data from in problem 2In a rising film evaporator, if the heat transfer coefficient is proportional V0.6,
Calculate the average force air discharge from a compressor to compress a tank of 1000 L 1 kg/cm2 to 5 kg/cm2 at 30°C 2 h.
Calculate the isothermal efficiency of compressor discussed in problem 4.Data from problem 4Calculate the average force air discharge from a compressor to compress a tank of 1000 L 1 kg/cm2 to 5
Calculate the volumetric efficiency discussed in problem 4, if it contain 4 single action cylinders.Data from problem 4Calculate the average force air discharge from a compressor to compress a tank
Calculate the energy required to remove 10% of water in a batch pan containing 10,000 L of water at 100°C.
The mean residence time in a tubular reactor is the length L divided by the average velocity v = q/π R2. Using the results from Problems 7.8 and 7.9, what can you say about the relative values of
Follow the approach in Section 5.7 to derive the equation for the dependence of concentration on spatial position in a tubular reactor of length L operating at steady state, in which the radius is R
Consider the optimal design problem in Section 7.3, but now suppose that the capital cost of the reactor increases with volume as Vα, α < 1. Derive the algebraic equation for the optimal
Derive Equation 5.3 directly by doing a steady-state mass balance with a control volume that includes both VR and VP.
The following data were obtained in a cylindrical vessel of diameter 2.54 cm (1.0 in.) that was allowed to drain through an orifice of diameter 0.109 cm (0.043 in.).a. Fit the equation q = kh to the
Consider the process in Example 13.4. Can you reduce the required area substantially by changing the coolant flow rate?Example 13.4We must reduce the temperature of a small process steam flowing at 2
The formation of sugars from biomass is of considerable interest in a variety of applications, including energy alternatives to fossil fuel. Harris and Kline studied the formation of glucose from
Kinetic data for the reaction between sulfuric acid and diethyl sulfate are given in Examples 6.1 and 6.4. Suppose that V = 25.4 L, qAf = qBf, cAf = 11.0 g-mol/L, cBf = 5.5 g-mol/L, and the required
An irreversible first-order decomposition reaction A → M is carried out in a CFSTR, with k = 0.005 min−1. The feed composition cAf is 0.2 g-mol/L, and the desired production rate of product is 50
Select a chemical engineer whose work looks interesting to you, and do a search on his/her publications to get a broader picture. (Your library will have access to several scientific search engines.
Go to your own chemical engineering department’s home page and see what kind of scholarly work your faculty members are doing.
Select a topic of interest to you that involves chemical engineering, do some reading, and write a short review of the outstanding issues. Here are a few suggestions of very broad and socially
A wedge-shaped tank is filled and emptied at constant flow rates qf and qe, respectively. The liquid density is a constant at all times. The liquid height is h0 at t = 0. Find the height at any
Select a chemical that interests you and learn what you can about its production and uses.
The system shown in Figure 2P.2 might be used to load ore onto barges for shipment. Let W1 be the constant mass flow rate of ore onto the barge, and letMbe the mass of ore at any time. After the pile
Select a process that interests you and learn what you can about its creation and subsequent development. (Fluid catalytic cracking is a good choice if you don’t have another.)
Suppose that we wish to use a combination of feedback and feedforward control in the form qe = q∗ + Kf b(h − h∗) + KffQ(t).a. Show that you obtain perfect control (h = h* at all times) for Kff
A chemical operator is draining a tank originally full of crude oil. The tank measures 0.91 m (3 ft) in diameter. The operator opens a valve with a 3.18 cm (1–1/4in.) diameter in the tank base. He
A tank is filled at a constant flow rate qf, while it empties through a valve for which the flow rate is equal to kh1/2. Will this system come to a steady state (dV/dt = 0)? If so, what is the height
The following population data are available for Iceland and the Faroe Islands (lumped together, because Iceland’s independence from Denmark came only in 1944):Neglecting immigration and emigration,
The following are population data for theUnited States during the period 1930–1960:Immigration and emigration data are not included. Construct a model of population growth and check against the
A water clock is a vessel that has a shape such that the liquid level h decreases at a constant rate. In this way, water level markings can be easily calibrated with elapsed time. Water clocks were
Banks often advertise continuous compounding of interest on savings accounts, by which they mean that interest is added continuously to the account at a rate equal to the product of the current
The Mediterranean Sea exchanges water with the Atlantic Ocean. Fresh water inflow to theMediterranean is approximately 30,000 m3/s and evaporation occurs at a rate of approximately 80,000 m3/s. The
A well-stirred process vessel contains 1.7 m3 (450 gallons) of a solution of water and 34 kg of sodium chloride at the time that a pure water feed stream is introduced. Find the salt concentration at
According to OSHA, a level of chlorine in the air of 3ppmwill cause impairment. Suppose there is a constant source of chlorine of 4 g/hr in a room that is ventilated at a rate of 250 m3/s. What is
The OSHA recommendation for laboratory ventilation is four to twelve room air changes per hour. Approximately how long does it take to reach a steady-state concentration in a laboratory with a
A soft drink process requires mixing sugar and water continuously in a 250 m3 tank. We have one measurement of the density of sugar: At a concentration of 207.5 kg/m3 the density is 1,083 kg/m3. The
Four people enter an empty smoking lounge that has a volume of 50 m3 and is ventilated at a rate of 120 m3/hr. Each person smokes about two cigarettes an hour, and each cigarette produces about 40 mg
A well-dispersed mixture of solids and liquid is to be concentrated by being pumped through a tank with a porous plate at the bottom through which pure liquid may pass, as shown schematically in
Suppose that the data in Table 6.1 for the reaction of sulfuric acid with diethyl sulfate in aqueous solution are described by a rate of the form r = kcAn. Investigate the consequences of an error of
A dialysis system is set up to reduce the concentration of a solute from 100 g/L to 1 g/L. The membrane permeability is 0.001 m/s, and the raffinate flow rate is 0.25 L/min. The permeate stream
Consider a dialysis system in which the membrane has a permeability of 1/3 cm/min and the total available membrane area is 2,700 cm2. The raffinate feed rate is 300 mL/min and the total permeate flow
Consider a continuous countercurrent dialysis system that uses a flat membrane with a width of 25 cm and a permeability of 1/3 cm/min. The raffinate and permeate feeds are 300 mL/min and 900 mL/min,
Data for the decomposition of dibromosuccinic acid (2,3-dibromo-butanedioic acid), C2H2Br2(COOH)2, in a batch reactor are shown in Table 6.P1 as mass of acid remaining as a function of time. Find the
Reconsider the data in Table 6.1 for the reaction between sulfuric acid and diethyl sulfate, and suppose that you believe that the forward reaction rate is actually of the form r = k′cA. Test this
The data in Table 6.P3 are for reactant A in the irreversible reaction A + βB → products. The initial concentrations are believed to be in stoichiometric balance. Estimate the reaction order and
The reaction ClO3− + 3H2SO4 → Cl− + 3SO4= + 6H+ in 0.2N H2SO4 was studied in 1932 by Nixon and Krauskopf, who reported the data in Table 6.P2. Find a rate expression that is consistent with the
Show that Equation 6.11a for the reaction A + B → μM with equal initial concentrations of A and B (ψ = 0) follows from Equation 6.11b for unequal initial concentrations in the limit ψ →
The hydrolysis of acetic anhydride in excess water to form acetic acid, (CH3CO)2O + H2O→2CH3COOH, was studied by Elridge and Piret, who found that the rate at 15◦C is first order in anhydride,
The reaction acetic acid (A) + butanol (B)→ester + water was studied by Leyes and Othmer, who found the data in Table 6.P4 at 100◦C in the presence of 0.03 percent sulfuric acid. The initial
The saponification of the ester propargyl acetate,with base (B, OH–) was studied by Myers, Collett, and Lazzell using a conductivity technique to follow the course of the reaction. Conductivity,
Consider the full data set in Table 6.5 for the reversible reaction between sulfuric acid and diethyl sulfate and test the applicability of each of the following rate expressions:Table
The reaction A → products is believed to follow a rate expressionHow will the concentration in a batch reactor change with time? Discuss the limits k2cA0 ≫ 1 and k2cA0 ≪ 1. TA- ICA = 1+k₂CA
The chemical reaction sequence A→M→S takes place in a CFSTR. You may assume that the reactions are irreversible and first order, with rate constants k1 for the reaction A→M and k2 for the
The irreversible reaction A → products is believed to be nth order in the concentration of A. Devise a strategy for obtaining the order and rate constant by carrying out steady-state experiments in
The decomposition of the carcinogen N-nitrosodiethylamine (NDEA) in water was shown in Example 6.3 to be first order when exposed to ultraviolet radiation at an intensity of 1 mW/cm2, with a rate
Generalize your result to Problem 7.7 as follows: A first-order reaction is to be carried out in a batch reactor and in a CFSTR to achieve a relative reduction RR in concentration. (In Problem 7.7,
In Equation 9.2, show that ∂(cA/cAf )/∂k2 > 0.Equation 9.2 СА C Af || 1 + k20 1+ (ki + kz)0
Derive Equation 10.29 by carrying out a mass balance for species A on a control volume that encompasses both Phase I and Phase II. Then assume that A is in equilibrium between the two phases and
In analogy to the treatment in Section 5.7, derive the equations describing a countercurrent membrane reactor in which the reversible first-order reaction A⇄ M is carried out.Section 5.7:The staged
One step in the preparation of nicotine sulfate from tobacco is the extraction of nicotine from aqueous solution by kerosene. Table 10.P1 shows equilibrium data for the distribution of nicotine
The data in Table 10.P2 are from a batch experiment measuring the distribution of octanoic acid between an aqueous phase consisting of a solution of corn syrup in water and an organic xylene phase.
A useful model of interfacial mass transfer makes three assumptions:(i) There is a difference between the concentrations of A at the interface, denotedcI∗A and cII∗A in Phases I and II,
Trace amounts of phenol are to be extracted from an aqueous stream (Phase I) using pure xylene as a solvent. From data in the Chemical Engineers’ Handbook we have M = 1.4.a. What xylene/water flow
a. What is the minimum solvent flow rate that can be used in countercurrent operation to remove 75 percent of the acetic acid in the process stream described in Problem 11.1?b. How many
Repeat Problem 11.1 without the assumption of negligible solute transfer.Problem 11.1It is necessary to process 100 kg/min of a water stream containing 15 percent acetic acid by weight. How much acid
In an experiment carried out by one of our undergraduate students, a water stream and a chloroform stream** were fed continuously to a 1,000 cm3 cylindrical tank with a cross-sectional area of 81
Data for the distribution of picric acid in a benzene-water system at 15◦C are shown in Table 10.P3. (Note that the concentrations are in molar units, and that Nerst’s “law” clearly does not
It is necessary to process 100 kg/min of a water stream containing 15 percent acetic acid by weight. How much acid can be extracted in a single equilibrium stage with pure isopropyl ether using(a)
10 kg of water is heated to raise the temperature by 7◦C. How high would the liquid have to be lifted to change the total energy by the same amount? To what velocity must we accelerate the liquid
Repeat the calculation in Problem 10.3 with the assumption that the heat capacity of liquid toluene is constant, using the values at(a) 10◦C;(b) 35◦C;(c) 60◦C. How large is the error in each
The heat capacity of liquid toluene at atmospheric pressure is well represented in the range 280 K to 360 K by the empirical equation cp = -1.17 + 9.61 × 10−3T, where T is in K and cp is in J/g
What is the change in enthalpy of 1 kg of water when the temperature is changed from 25◦C to 10◦C?
The data in Table 11.P2 were obtained for the recovery of methyl ethyl ketone from water by solvent extraction. 500 kg/hr of an aqueous 18 percent by weight ketone solution is to be processed, with
Trace amounts of phenol are to be extracted from an aqueous stream using pure xylene, for which M = 1.4 . What is the minimum amount of xylene required to remove 90 percent of the phenol from the
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