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engineering
chemical engineering
Questions and Answers of
Chemical Engineering
If the liquid junction potential for a combination \(\mathrm{pH}\) electrode drifts by \(5 \mathrm{mV}\), what is the relative error in the apparent \(\mathrm{H}^{+}\)concentration?
A solution of TISAB with \(1 \mathrm{M} \mathrm{NaCl}\) is available to treat drinking water samples for fluoride determination using a fluoride ISE and a \(\mathrm{Ag} / \mathrm{AgCl}\) reference
Consider using an ISE for determining bromide ion based on \(\mathrm{AgBr} / \mathrm{Ag}_{2} \mathrm{~S}\) crystalline membrane. The \(K_{\mathrm{sp}}\) for \(\mathrm{AgBr}\) is \(7.7 \times
What is the maximum activity of sodium ions that can be tolerated in order to measure \(\mathrm{K}^{+}\)ions at activities as low as \(1 \times 10^{-4} \mathrm{M}\) with at most a \(10 \%\) error
Your colleague is preparing to perform some field measurements of chloride in stream water using an ISE. He is aware that he cannot use measurements of standards in the lab at \(20^{\circ}
In experiments with standard solutions, \(\mathrm{a} \mathrm{Li}^{+}\)ISE gave a calibration curve of\[E=0.39+(0.0577) \log \left[\mathrm{Li}^{+}ight]\]An analyst assumed that the sensitivity of the
A well-used nitrate ISE was being used to test some ground water samples for possible leaching from a hazardous waste site. A percent recovery procedure was performed to decide whether a standard
Refer to Table 4.4 of selectivity coefficients for cations that interfere with the creatinium ISE described. At what concentration of creatinine would \(0.3 \mathrm{M}\) ammonium interfere to cause a
For a membrane without an ionophore, why is the membrane potential more sensitive to chlorate ion than sulfate ion?
In addition to preparation of the standard solutions and treatment of the sample solutions, a good environmental analysis requires various control solutions that check the reliability of the
Imagine that you were asked to set up a flow injection system in order to measure \(\mathrm{K}^{+}\)ion levels in blood samples in a hospital lab. List at least five different challenges for
Here are data from a \(\mathrm{pH}\) titration of potassium hydrogen phthalate with \(\mathrm{NaOH}\) using an automated titrator. Only data for part of the titration has been provided. Prepare a
Why is the filling port for the outer reference chamber of a combination glass electrode kept open during measurements?
A chronoamperometry experiment was performed on a \(4.00 \mathrm{mM}\) solution of an iron(III) complex at \(25^{\circ} \mathrm{C}\) using a platinum electrode with an area of \(0.075
A \(33.6 \mathrm{mg}\) sample of a freeze-dried enzyme preparation was injected into a Karl Fisher coulometric titrator and the endpoint was reached in 27.6 seconds at a current level of \(150.7
From the CV below, estimate the formal potential for the redox couple. Anodic current Cathodic current 5.0 4.0 3.0 2.0 1.0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -1.0 Eapplied -2.0 -3.0
For the voltammogram in Problem 5.3, determine whether the one-electron transfer process is reversible in the electrochemical sense.Data from Problem 5.3From the CV below, estimate the formal
Does the voltammogram in Problem 5.3, indicate any possibility that the reduced or the oxidized form is unstable under the conditions in this solution? Support your answer with a calculation.Data
If the experiment in Problem 5.3 was recorded using a saturated calomel reference electrode at \(25^{\circ} \mathrm{C}\), what is the value of \(\mathrm{E}^{\circ \prime}\) for the redox couple on
If for a cyclic voltammogram the \(E^{\mathrm{O} \prime}\) for quinone, \(Q\), appears at a \(+0.220 \mathrm{~V}\) at a platinum electrode (versus silver/silver chloride ref. electrode) at
An organic compound produced the CV labeled A in an aqueous phosphate buffer on a glassy carbon electrode after polishing the electrode and cleaning it in a sonicating bath with deionized water.
A staircase voltammogram was recorded for a \(1 \times 10^{-4} \mathrm{M}\) solution of a reversible iron complex in which the voltage was stepped \(5 \mathrm{mV}\) every \(10 \mathrm{~ms}\) sampling
Imagine that your colleague is interested in performing anodic stripping analysis of \(\mathrm{Pb}\) in drinking water and has been frustrated that he has not achieved the detection limits necessary
Give a chemical explanation of why gold and platinum working electrodes are used as working electrodes for pulse amperometric detection (PAD) rather than glassy carbon.
A cyclic voltammogram of p-aminophenol in \(0.01 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) was recorded with a carbon paste electrode scanning from \(0 \mathrm{~V}\) in the positive direction. The
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
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