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engineering
chemical engineering
Questions and Answers of
Chemical Engineering
One way to determine whether a current signal in a cyclic voltammogram is the result of a freely diffusing analyte or an electroactive compound attached to the electrode surface is to perform a scan
The cyclic voltammogram for methyl benzoate was recorded in dimethylformamide (DMF) using a platinum working electrode (lower curve). The product appears to be a singly-charged aryl radical. The
For a RDE at \(500 \mathrm{rpm}\) a \(0.1 \mu \mathrm{M}\) solution of an iron complex gave a limiting current of \(2.73 \mathrm{nA}\). What would be the limit of detection for this complex if the
What is the voltage at point \(\mathrm{A}\) in the following circuit? V bat +2 V 100 500 3000 2
Calculate the current through the \(100 \Omega\) resistor in the diagram for Problem 7.2.Data from Problem 7.2 What is the voltage at point \(\mathrm{A}\) in the following circuit? V bat +2 V 100
Derive the algebraic expression for the effective resistance in the circuit below. Vbat = +5 V Ra R Re
For the circuit in Problem 7.4, let \(R_{\mathrm{a}}=500 \Omega, R_{\mathrm{b}}=400 \Omega\), and \(R_{\mathrm{c}}=300 \Omega\). Calculate the effective resistance in the circuit.Data from Problem
For the conditions given in Problems 7.4 and 7.5, calculate the current passing through each of the resistors \(R_{\mathrm{a}}, R_{\mathrm{b}}\), and \(R_{\mathrm{c}}\).Data from Problem 7.5For the
For the circuit in the diagram below, calculate the output voltage for an input current, \(i_{\text {in }}\), of \(15 \mathrm{nA}\) and a feedback resistance, \(R_{\mathrm{f}}\), of \(200 \mathrm{k}
Draw an op amp circuit capable of producing an output of \(0.1 \mathrm{~V}\) for a current signal of \(20 \mathrm{nA}\) using two stages.
In the circuit below,(a) What is the output voltage when \(V_{\text {in }}=0.100 \mathrm{~V}\) for an ideal amplifier?(b) What input voltage would give an output of \(-0.500 \mathrm{~V}\) ? Vin 1000
In Figure 7.12 only two of the three leads to the potentiometer are connected. Explain what the potentiometer's purpose is and how it functions in that circuit.Figure 7.12 Copper wire Non-conducting
Draw a modification of the circuit in Problem 7.9 so that it would be possible to amplify a signal from a chloride ion selective electrode (ISE) by a factor of 5 without draining significant
Describe the two most important considerations in choosing the concentration of the \(\mathrm{KCl}\) solution for the internal filling solution and the salt bridge for a silver/silver chloride
Calculate the reference potential for a silver/silver chloride reference electrode for a solution that is \(0.100 \mathrm{M}\) chloride activity.
In a three-electrode potentiostat, with a silver/silver chloride reference electrode (with \(3 \mathrm{M} \mathrm{KCl}\) ), what voltage should be applied at \(V_{1}\) in order to reduce ferricyanide
In a three-electrode potentiostat, the counter or auxiliary electrode (AE) carries current so that the reference electrode (RE) does not need to. Under what circumstances does the auxiliary electrode
Derive the general mathematical equation that relates the output voltage, \(V_{\text {out }}\), to the input signal, \(V_{\text {in }}\). Rin Rf Vin + V out
A gas absorption tower is used to absorb sulfur dioxide from air into water at 20°C and 2.0 atm absolute pressure. At the top of the tower, the water is 100% pure and the gas contains 5.0 mol % SO2.
An absorption tower was designed and built to remove 80% of a pollutant A from air fed into the bottom of the tower at a mole fraction of 0.01. The absorbing liquid is pure water and the liquid flow
A wastewater stream flowing at the rate of 600 GPM (gallons per minute) and containing 10 ppm (parts per million by weight) benzene is to be stripped with air in a packed column operating at 25°C
The performance of a packed absorption tower is to be evaluated from the following experimental results. The test tower is 6 ft in diameter and is packed to a depth of 10 ft with 1-in. metal Pall
A gas absorption column is to be designed to absorb SO2 from air using pure water as the absorbent. The inlet air contains 5.0 mol% SO2 and flow at the rate of 30.0 mol/s and it is desired to remove
It is desired to recover ammonia from an air stream at 1 atm by absorption in water in a tower packed with 2-in. plastic Flexi-saddles operating at 30°C. The inlet gas contains 20 mol% ammonia and
A gas absorption column is to be designed to remove 90.0% of the ammonia from an air stream containing 2.0 mol% ammonia. The absorbent is pure water. The column is to be packed with 50 mm metal Pall
The following problem is based on data and analyses of ternary gas diffusion for the system CO2(A)/H2O (B)/H2 (C) at 40°C and 155 mmHg absolute pressure. (a) Estimate the binary diffusion
A diaphragm diffusion cell is used to determine diffusivities in aqueous solutions by measuring the mass transfer flux across an inert macroporous slab that separates two well-mixed compartments. In
Lysine is an essential amino acid used in many applications, including animal and human foods and pharmaceuticals. A sulfonated poly(styrene-divinylbenzene) cation-exchange resin with an 8% degree of
Spherical particles are used in many practical applications including adsorption and ion exchange. Mass transfer in such particles can be described starting with a differential material balance in
A thin porous metal plate, 0.3 m long and very wide, is placed in a stream of dry air at 500°C and 1 atm absolute pressure, flowing at a velocity of 15 m/s parallel to the 0.3 m dimension. Liquid
A forced-draft cooling tower is to be designed to cool water from 35°C to 15°C in a dry, cool climate where the air is at 20°C with a relative humidity of 30%. The design air mass velocity is to
A counter-current gas-absorption column is to be designed to remove CO2 from an inert gas stream by reaction with an amine solution at 20°C. At this temperature, CO2 reacts with the amine according
Measurements of the rate of absorption of CO2 in water and in aqueous NaOH solutions are to be used to determine the mass transfer coefficient, , and the gas-liquid interfacial area,a, in a
Hydrogen sulfide (H2S) is to be removed from natural gas by absorption into amine solutions in a process known as natural gas sweetening. Experiments were done to measure the rate of absorption of
The thermal conductivity of a certain solid material is k = 25 W/m K. At a certain point and time in a block of this material sketched in Fig.P.1.1, the temperature is 65°C, the temperature gradient
A condenser at the top of a distillation column operated at 1 atm absolute pressure is to be designed to condense 0.50 kg/s of essentially pure isopropyl alcohol using cooling water entering the
Floor heating is used to keep a room at a toasty 25°C. On a cold day, the room loses heat through the walls, ceilings, door, and windows at the rate of 2,000 W. The heated floor area is 30 m2. The
Bona fide Italian pizza is cooked in a domed brick oven. A wood fire is first lit inside the dome, which brings the brick temperature to something around 800°F. The fire is then pushed aside prior
Estimate the thermal conductivity of NH3 gas at 450 K and 1 atm absolute pressure and compare your estimate with the experimental value.
Estimate the thermal conductivity of CO2 at 365 K and 1 atm absolute pressure. Then use this value to find the thermal conductivity at 365 K and 200 atm absolute pressure.
Estimate the thermal conductivity of a gas mixture containing 40 mol% ammonia and 60 mol% N2 at 400 K and 1 atm absolute pressure.
Estimate the thermal conductivity of liquid isopropyl alcohol at 300 K and compare your estimates with the experimental value available in Section 2 of Perry’s Chemical Engineers’ Handbook.
Estimate the thermal conductivity of liquid mixtures of n-hexane and n-decane at 295 K and 335 K and 1 atm absolute pressure as a function of the mole fraction of n-hexane and compare your estimate
A silica-based catalyst particle has a porosity εp = 0.60. Estimate its thermal conductivity at 25°C if the pores are (a) filled with air at 1 atm and(b) filled with liquid water.
The thermal properties of animal and human tissue have been extensively characterized, and an ample database is available at
Double-pane glass windows, designed to reduces heat losses, consist, as the name implies, of two glass panes separated by a thin gap filled with dry air and sealed. Let’s compare the efficiency of
Serpe has reported on the development of“smart windows,” where the gap between two glass panes is filled with an aqueous solution containing hydrogel particles made of
The walls of a cold-storage room kept at 8°F are insulated with a 4-in. layer of cork. The external air is at 72°F and has a dew point of 60°F.Since cork is porous, air diffuses across the
The design of an astronaut’s glove requires that you select the thickness of insulation needed to keep the skin surface temperature at 25°C for long periods of time when the outer surface of the
An insulated cardboard box is to be designed to transport a labile vaccine product that has to be kept at −78°C in areas where lowtemperature refrigeration is not widely available. The box is a
For a class demonstration project, I placed an empty stainless-steel pan (k =15 W/m K) onto a hot plate with its temperature set at 150°C as shown in Fig. P.3.6. After a few minutes, I asked the
A cylindrical exhaust duct has a constant inside temperature of 650°F and is insulated on the exterior with a 4-in. layer of rock wool, which has an outer surface temperature of 95°F. The duct has
The thermal conductivity of an opaque insulating material is to be determined by lighting a 5-W light bulb inside a hollow sphere made of that material and measuring the surface temperatures. The
Liquid nitrogen loaded into an insulated tank at 1 atm absolute pressure is kept at the boiling point by allowing a small amount of it to gradually evaporate and flow out of the tank. In order to
The proposed design of a fuel element for a nuclear power reactor consists of 2-in.-diameter cylindrical fuel core surrounded by a 0.25-in.-thick aluminum-alloy cladding. The outside surface of the
A cube, 1.0-in. long on each side, is constructed of equal-sized, alternating parallel layers of copper and Pyrex glass. There are five layers of copper and five layers of glass. A question has
An electrically heated glove consists of a flat thin-sheet electrode embedded within a 0.01 m layer of an insulating material with a thermal conductivity of 0.02 W/m K, which is directly in contact
Consider a slab-shaped graphite electrode that is 3 ft long, 3 in.wide, and 0.5 in. thick. A voltage difference of 24 V is applied across the 3-ft length. Assuming that the temperature is uniform
Heat is to be provided to a small room with the finned heater sketched in Fig. P.4.1. Circulating hot oil keeps the base of the fins at 140°F. The fins are made of iron with k = 40 BTU/h ft °F, and
To increase heat dissipation from a long tube with a 3.0-cm outer diameter, 12 longitudinal rectangular fins made of aluminum (k = 250 W/m K) are attached to the outer surface of the tube projecting
A cylindrical power transistor that generates heat at a constant rate is kept cool by a set of 12 rectangular aluminum fins mounted radially as sketched in Fig. P.4.3. The transistor is 1 cm in
A 45-W power integrated circuit chip mounted on an insulated circuit board is to be kept at its maximum operating temperature of 70°C using five identical straight rectangular aluminum-alloy fins (k
A metal pot holding boiling water has a handle made of an uninsulated hollow, stainless steel tube (k = 20 W/m K) with inner and outer diameters of 1.6 cm and 2.0 cm, respectively, and is 25 cm long.
A large metal pot containing fondue (melted cheese) held at 120°C is to be placed on a wooden table supported on a trivet with four vertical legs. The legs are solid cylindrical rods with a diameter
A thermocouple well, sketched in Fig. P.4.7, is used to measure the temperature of the air flowing inside a metal duct at a velocity of 10 m/s.The well consists of a cylindrical copper tube (0.01 m
The liquid phase reactor shown in Fig. P.4.8 is operated at 250°C and is agitated with a propeller mounted on a 10-cm-diameter steel shaft with a thermal conductivity k = 50 W/m K. The agitator
Consider a straight fin with the trapezoidal shape sketched in Fig. P.4.9. Assuming that the temperature in the fin is only a function of the axial coordinate x (i.e., it is uniform at each vertical
An air-cooled utility engine needs to dissipate 2,000 W of heat in order to operate at a steady temperature of 150°C when the ambient temperature is 25°C. The engine block can be represented as a
We want to bond together two slabs of a solid material, each with a thickness of 1.5 cm, to form a laminate by using a thin layer of a thermosetting glue, which fuses and forms a bond between the two
A stainless-steel plate, 1.0 m2 in area and 5.0 cm thick, is to be attached to a glass substrate with a thermosetting glue. For this purpose, a thin layer of the glue is applied to the glass and the
A long, cast-iron cylinder 0.2 m in diameter and initially at 95°C is cooled by contacting it with a stream of liquid water at a constant temperature of 25°C. The convective heat transfer
It is March 7th, the first day of Spring break, and you have not made it quite to beach destination. Perhaps you could have, except for that sheriff with the radar trap—but that is behind you as
A solid teflon cylinder 0.05 m in diameter and 1 m in length initially at a uniform temperature of 100°C is cooled by blowing air at 20°C over it.The Biot number is Bi = 2.0. (a) Determine the time
Pyrex-glass spheres 2 cm in diameter and initially at 100°C are cooled by a stream of air at 30°C. The convective heat transfer coefficient is estimated to be 60 W/m2 K. (a) Determine the
A long concrete beam with a rectangular cross-section measuring 8× 12 in. is exposed to a temperature of 1,500°F in a fire. Using Newman’s rule, determine the time of exposure needed for the
A long cylindrical fiber of a plastic material with thermal conductivity k = 0.13 W/m K, density ρ = 1,400 kg/m3, and heat capacity Cp = 1,050 J/kg K is continuously extruded and cooled by pulling
A soft drink in a cup can be cooled without dilution using chilled plastic spheres that are 1.0 cm in diameter instead of ice. Assume that 300 mL of the spheres initially at −20°C are added to 300
It has been claimed that “smart,” hydrogel-filled double-pane windows can be used to shift energy usage in buildings to off-peak times by delaying the heat transfer as a result of the heat
Air at 200°F and 1 atm absolute pressure is to be cooled to 70°F by passing it through a 2-in. ID copper pipe submerged in an ice bath. The air flow rate is 70 lb/h. Neglecting the heat transfer
We want to cool a solution containing 100 mg/mL of a monoclonal antibody from an initial temperature of 25°C to 10°C by having the solution flow through a coil of stainless-steel tubing immersed in
Quartz-glass spheres 2 cm in diameter and initially at 70°C are cooled by a large toluene stream at 20°C flowing over the spheres at a velocity of 0.01 m/s. Determine: (a) The heat transfer
A 10-volt (DC) electrical potential difference is applied to a 1 m long× 1 mm diameter nichrome (80% Ni, 20% Cr) wire. The wire is suspended horizontally in air at 20°C which flows across the wire
Two options are being considered to cool a can of a soft drink from an initial temperature of 35°C to a maximum temperature of 15°C as quickly as possible. The can is 5 cm in diameter and 20 cm
A cylinder of a radioactive solid, 1.5 cm in radius and 2 m long, is encased in a cylindrical shell of pyrex glass, 3.0 cm in outside radius. The radioactive core generates heat at the steady rate of
Plastic spheres, 0.02 m in diameter and initially at 120°C, are cooled by allowing them to drop into a large pool of water at 20°C. The spheres have a density of 1050 kg/m3, a heat capacity of 900
A square slab of pure silicon to be used to manufacture microelectronics components is to be cooled in air at 25°C from an initial temperature of 200°C to 30°C. The slab is 0.5 m on a side and 5
Redo problem P.6.4 assuming that there is no forced convection, i.e., all of the heat transfer is by natural convection.Data From Problem P.6.4:A 10-volt (DC) electrical potential difference is
A double-pipe heat exchanger is to be designed to cool 5.5 gal/min of a hot oil from 250°F to 120°F using 11 gal/min of cooling water available at 70°F. The exchanger is to consist of 12-ft-long
Assume that the oil in problem P.7.1 is an organic liquid coming from a chemical reactor. It is necessary to “quench” this hot oil as quickly as possible to stop the reaction and prevent its
Dolphins and other marine mammals are able to maintain a surprisingly high body temperature even though they are swimming in ocean water at 4°C. Since the dolphin tail has a large surface area, much
A shell and tube heat exchanger being used to heat 0.80 kg/s of oil from 27°C to 150°C is made of one hundred 1-in.-diameter 16-BWG-gage copper pipes (see Table 11-12 in Perry’s Chemical
Acetone vapor at 150°C and 1 atm absolute pressure enters the shell side of a vertical counter-current shell and tube heat exchanger with onetube pass and one-shell pass at the rate of 0.1 kg/s and
A shell and tube heat exchanger with two-tube passes consists of a total of 3,000 straight copper tubes inside a single shell. The tubes have an outer diameter of 2.5 cm and an inner diameter of 2.0
A liquid A is heated from 20°C to 60°C flowing on the tube side of a shell and tube heat exchanger at a flow rate of 44 kg/s. Another liquid B flowing on the shell side is cooled from 100°C to a
A shell and tube heat exchanger with one-tube pass and one-shell pass has been designed to cool a hot oil on the shell side from 70°C to 40°C using cooling water that on the tube side entering at
A shell and tube heat exchanger is to be designed to preheat the feed to a reactor with = 800 W/K from 20°C to 90°C using waste-saturated steam at 1 atm absolute pressure. The overall heat
Ozonization of water can be used to control odor and for disinfection.In the simple ozonizer sketched in Fig. P.8.1, air containing 5.0 mol % O3 is bubbled through water at 20°C flowing at the rate
Sampling by the local Department of Environmental Quality (DEQ)of the water in a small creek has revealed a steady concentration of a highly toxic chemical of 0.015 g/m3. At some distance upstream
Two glass bulbs are connected by a 0.2-m-long glass tube with a 0.001-m inner diameter. Initially, bulb 1 contains pure argon and bulb 2 contains pure xenon. Bulb 1 has a volume of 1 L. The absolute
Under certain conditions, evaporation of a solvent A from freshly-applied paint into air is controlled by diffusion. Assume that diffusion occurs through a thin film of stagnant air adjacent to the
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