Question: A typical simple infrared spectrophotometer covers

> Calculate the product concentrations versus time for a pseudo-first-order reaction with k’ = 0.015 s-1 and [A]0 = 0.005 M. Use times of 0.000 s, 0.001 s, 0.01 s, 0.1 s, 0.2 s 0.5 s, 1.0 s, 2.0 s, 5.0 s, 10.0 s, 20.0 s, 50.0 s, 100.0 s, 200.0 s, 500.0 s,

> The following data represent the product concentrations versus time during the initial stages of pseudo-first-order reactions with different initial concentrations of analyte [A]0: For each concentration of analyte, find the average initial reaction rat

> The enzyme monoamine oxidase catalyzes the oxidation of amines to aldehydes. For tryptamine, Km for the enzyme is 4.0 × 10-4 M, and vmax = k2[E]0 = 1.6 × 10-3 μM/min at pH 8. Find the concentration of a solution of tryptamine that reacts at a rate of 0.1

> Aluminum forms a 1:1 complex with 2-hydroxy-1-naphthaldehyde p-methoxybenzoylhydraxonal that exhibits fluorescence emission at 475 nm. Under pseudo-first-order conditions, a plot of the initial rate of the reaction (emission units per second) versus the

> Copper(II) forms a 1:1 complex with the organic complexing agent R in acidic medium. The formation of the complex can be monitored by spectrophotome try at 480 nm. Use the following data collected under pseudo-first-order conditions to construct a calibr

> What properties of a supercritical fluid are important in chromatography?

> Some ionization sources, known as soft ionization sources, do not produce as many fragments as an electron ionization source, which is a hard ionization source. Which type of ionization source (hard or soft) is more useful for structure elucidation? Whic

> Define: a) Supercritical fluid. b) Critical point. c) Two-dimensional thin-layer chromatography. d) Electrophoretic mobility. e) Critical micelle concentration. f) Electrical fff

> List the types of substances to which each of the following separation methods is most applicable: a) Supercritical fluid chromatography. b) Thin-layer chromatography. c) Capillary zone electrophoresis. d) Sedimentation fff. e) Flow fff. f) Micellar

> List the major advantages and limitations of FFF compared to chromatographic methods.

> Three large proteins are ionized at the pH at which an electrical FFF separation is carried out. If the ions are designated A2+, B+, and C3+, predict the order of elution.

> What determines the elution order in sedimentation FFF?

> Describe a major advantage of micellar electrokinetic capillary chromatography over conventional liquid chromatography.

> What is the principle of micellar electrokinetic capillary chromatography? How does it differ from capillary zone electrophoresis?

> The cationic analyte of Problem 32-14 was separated by capillary zone electrophoresis in a 50-cm capillary at 20 kV. Under the separation conditions, the electroosmotic flow rate was 0.65 mm s 21 toward the cathode. If the detector were placed 40 cm from

> A certain inorganic cation has a electrophoretic mobility of 6.97 × 10-4 cm2 s-1 V-1. This same ion has a diffusion coefficient of 7.8 × 10-6 cm2 s-1. If this ion is separated by capillary zone electrophoresis with a 50-cm capillary, what is the expected

> What is the principle of separation by capillary zone electrophoresis?

> What is the difference between a precursor ion and a product ion in tandem mass spectrometry?

> How could electroosmotic flow be repressed? Why would one want to repress it?

> What is electroosmotic flow? Why does it occur?

> What is the effect of pH on the separation of amino acids by electrophoresis? Why?

> For supercritical carbon dioxide, predict the effect that the following changes will have on the elution time in an SFC experiment. a) Increase the flow rate (at constant temperature and pressure). b) Increase the pressure (at constant temperature and

> Compare supercritical fluid chromatography with other column chromatographic methods.

> What important property of supercritical fluids is related to their densities?

> List some of the advantageous properties of super critical CO2 as a mobile phase for chromatographic separations.

> How do instruments for supercritical fluid chromatography differ from those for (a) HPLC and (b) GC?

> Describe the effect of pressure on supercritical fluid chromatography.

> Indicate the order in which the following compounds would be eluted from an HPLC column containing a reversed-phase packing: a) Benzene, diethyl ether, n-hexane. b) Acetone, dichloroethane, acetamide.

> Is it easier to couple a GC with a mass spectrometer or an HPLC? Why is this the case? What are the major difficulties in these couplings?

> Define (a) Dalton. (b) Quadrupole mass filter. (c) Mass number. (d) Sector analyzer. (e) Time-of-flight analyzer. (f) Electron multiplier.

> A single mixture containing only CHCl3 and CH2Cl2 was divided into five parts to obtain samples for replicate determinations. Each sample was dissolved in methanol and electrolyzed in a cell containing a mercury cathode. The potential of the cathode was

> Determine the number of ions undergoing electron transfer at the surface of an electrode during each second that an electrochemical cell is operated at 0.0175 A at 100% current efficiency and the participating ions are: (a) Univalent. (b) Divalent. (c) T

> A compound X is to be determined by UV/visible spectrophotometry. A calibration curve is constructed from standard solutions of X with the following results: 0.50 ppm, A = 0.24; 1.5 ppm, A = 0.36; 2.5 ppm, A = 0.44; 3.5 ppm, A = 0.59; and 4.5 ppm, A = 0.

> A solution with a “true” absorbance [A = -log(P0/P)] of 2.10 was placed in a spectrophotometer with a stray light percentage (Ps/P0) of 0.75. What absorbance A’ would be measured? What percentage error would result?

> The complex formed between Cu(I) and 1, 10-phenanthroline has a molar absorptivity of 6850 L cm-1 mol-1 at 435 nm, the wavelength of maximum absorption. Calculate (a) The absorbance of a 4.42 x 10-5 M solution of the complex when measured in a 1.00-cm c

> A solution containing the complex formed between Bi(III) and thiourea has a molar absorptivity of 9.32 x 103 L cm-1 mol-1 at 470 nm. (a) What is the absorbance of a 5.67 x 10-5M solution of the complex at 470 nm in a 1.00-cm cell? (b) What is the percen

> A 2.50-mL aliquot of a solution that contains 4.33 ppm iron (III) is treated with an appropriate excess of KSCN and diluted to 50.0 mL. What is the absorbance of the resulting solution at 580 nm in a 2.50-cm cell? See Problem 22-21 for absorptivity data.

> At 580 nm, the wavelength of its maximum absorption, the complex Fe(SCN)2+ has a molar absorptivity of 7.00 X 103 L cm-1 mol-1. Calculate (a) The absorbance of a 3.40 X 10-5 M solution of the complex at 580 nm in a 1.00-cm cell. (b) The absorbance of a

> Beryllium (II) forms a complex with acetylacetone (166.2 g/mol). Calculate the molar absorptivity of the complex, given that a 2.25-ppm solution has a transmittance of 37.5% when measured in a 1.00-cm cell at 295 nm, the wavelength of maximum absorption.

> A solution containing 5.61 ppm KMnO4 exhibits 55.3 %T in a 1.00-cm cell at 520 nm. Calculate the molar absorptivity of KMnO4 at this wavelength.

> Evaluate the missing quantities in the accompanying table. Where needed, use 200 for the molar mass of the analyte.

> Calculate the absorbances of solutions with half the transmittance of those in Problem 22-15. Absorbances of solutions in Problem 22-15: a) A = 0.565 b) A = 0.237 c) A = 0.514 d) A = 0.816 e) A = 1.032 f) A = 0.099

> Calculate the percent transmittance of solutions that have twice the absorbance of the solutions in Problem 22-14. Absorbance of the solution in problem 22-14: a) %T = 92.1% b) %T = 12.3 c) %T = 41.8 d) %T = 80.9 e) %T = 32.7 f) %T = 23.8%

> Convert the accompanying transmittance data to absorbances. (a) 27.2% (b) 0.579 (c) 30.6% (d) 15.29% (e) 0.093 (f) 79.6%

> Express the following absorbances in terms of percent transmittance. (a) 0.0356 (b) 0.909 (c) 0.379 (d) 0.092 (e) 0.485 (f) 0.623

> What are the units for absorptivity when the path length is given in centimeters and the concentration is expressed in (a) Parts per million? (b) Micrograms per liter? (c) Mass-volume percent? (d) Grams per liter?

> Calculate the wavelength of a) The sodium line at 589 nm in an aqueous solution with a refractive index of 1.35. b) The output of a ruby laser at 694.3 nm when it is passing through a piece of quartz that has a refractive index of 1.5

> Calculate the wavelength and the energy in joules associated with a signal at 220 MHz

> Calculate the frequency in hertz and the energy in joules of an X-ray photon with a wavelength of 1.66 Å

> A sophisticated ultraviolet/visible/near-IR instrument has a wavelength range of 189 to 2900 nm. What are its wavenumber and frequency ranges?

> Calculate the wavelength in centimeters of (a) An airport tower transmitting at 118.6 MHz. (b) A VOR (radio navigation aid) transmitting at 117.95 kHz. (c) An NMR signal at 105 MHz. (d) An infrared absorption peak with a wavenumber of 1550 cm-1.

> What experimental factor places a limit on the number of significant figures in the response of a membrane electrode?

> Calculate the frequency in hertz of (a) An X-ray beam with a wavelength of 2.65 Å. (b) An emission line for manganese at 403.1 nm. (c) The line at 694.3 nm produced by a ruby laser. (d) The output of a CO2 laser at 10.6 μm. (e) An infrared absorption pea

> How does an electronic transition resemble a vibrational transition? How do they differ?

> What is the purpose of the electrodeposition step in stripping analysis?

> Why are stripping methods more sensitive than other voltammetric procedures?

> Why is it necessary to buffer solutions in organic voltammetry?

> Why is the reference electrode placed near the working electrode in a three-electrode cell?

> Why is a high supporting electrolyte concentration used in most electroanalytical procedures?

> Define (a) Voltammograms. (b) Hydrodynamic voltammetry. (c) Nernst diffusion layer. (d) Dropping mercury electrode. (e) Half-wave potential. (f) Limiting current.

> Distinguish between (a) Voltammetry and amperometry. (b) Linear-scan voltammetry and cyclic voltammetry. (c) Differential-pulse voltammetry and square-wave voltammetry. (d) A rotating disk electrode and a ring-disk electrode. (e) A limiting current and

> (a) What are the advantages of performing voltammetry with microelectrodes? (b) Is it possible for an electrode to be too small? Explain your answer

> List several sources of uncertainty in pH measurements with a glass/calomel electrode system.

> An unknown cadmium (II) solution was analysed polarographically by the method of standard additions. A 25.00-mL sample of the unknown solution produced a diffusion current of 1.86 μA. Following addition of a 5.00-mL aliquot of 2.12 x 10-3 M Cd2+ standard

> It has been suggested that many polarograms can be obtained on a solution without depleting the electroactive analyte. Suppose that in a polarographic experiment we monitor the limiting current for 45 minutes in 60 mL of 0.08 M Cu2+. If the average curre

> Sulfate ion can be determined by an amperometric titration procedure using Pb2+ as the titrant. If the potential of a rotating mercury film electrode is adjusted to -1.00 V versus SCE, the current can be used to monitor the Pb2+ concentration during the

> Quinone undergoes a reversible reduction at a voltammetric working electrode. The reaction is (a) Assume that the diffusion coefficients for quinone and hydroquinone are approximately the same, and calculate the approximate halfwave potential (versus SC

> Suggest how Equation 21-13 could be used to determine the number of electrons n involved in a reversible reaction at an electrode.

> List the advantages and disadvantages of the hanging mercury drop electrode compared with platinum or carbon electrodes.

> What experimental variables affect concentration polarization in an electrochemical cell?

> How does a current in an electrochemical cell affect its potential?

> Describe three mechanisms responsible for the transport of dissolved species to and from an electrode surface.

> Briefly define (a) Ohmic potential. (b) Overvoltage. (c) Controlled-potential electrolysis. (d) Coulometric titration. (e) Current efficiency. (f) Potentiostat.

> Why is it necessary for the glass in the membrane of a pH-sensitive electrode to be appreciably hygroscopic?

> Briefly distinguish between (a) Concentration polarization and kinetic polarization. (b) A reference electrode and a working electrode. (c) Diffusion and migration. (d) An ampere and a coulomb. (e) The electrolysis circuit and the control circuit for con

> The nitrobenzene in 300 mg of an organic mixture was reduced to phenylhydroxylamine at a constant potential of −0.96 V (versus SCE) applied to a mercury cathode: The sample was dissolved in 100 mL of methanol. After electrolysis for 30

> Electrolytically generated I2 was used to determine the amount of H2S in 100.0 mL of brackish water. Following addition of excess KI, a titration at a constant current of 56.8 mA required 9.13 minutes. The reaction was Express the results of the analysi

> The CN− concentration of 10.0 mL of a plating solution was determined by titration with electrogenerated hydrogen ion to a methyl orange end point. A color change occurred after 3 minutes and 55 s with a current of 57.5 mA. Calculate the number of grams

> A 0.1330-g sample of a purified organic acid was neutralized by the hydroxide ion produced in 5 minutes and 24 s by a constant current of 300 mA. Calculate the equivalent mass of the acid in grams.

> Calculate the time needed for a constant current of 1.25 A to deposit 0.550 g of (a) Tl(III) as the element on a cathode. (b) Tl(I) as Tl2O3 on an anode. (c) Tl(I) as the element on a cathode.

> Calculate the time needed for a constant current of 0.8510 A to deposit 0.250 g of Co(II) as (a) Elemental cobalt on the surface of a cathode. (b) Co3O4 on an anode. Assume 100% current efficiency for both gases.

> A solution is 0.200 M in each of two reducible cations, A and B. Removal of the more reducible species (A) is deemed complete when [A] has been decreased to 1.00 × 10−5 M. What minimum difference in standard electrode poten

> Electrogravimetric analysis with control of the cathode potential is proposed as a means for separating Bi3+ and Sn2+ in a solution that is 0.250 M in each ion and buffered to pH 1.95. (a) Calculate the theoretical cathode potential at the start of depos

> Describe the source of pH dependence in a glass-membrane electrode.

> A solution is is 0.0350 M in BiO+ and 0.0250 M in Co2+ and has a pH of 2.50. (a) What is the concentration of the more easily reduced cation at the onset of deposition of the less reducible one? (b) What is the potential of the cathode when the concentra

> A solution is 0.200 M in Co2+ and 0.0650 M in Cd2+. Calculate (a) The Co2+ concentration in the solution as the first cadmium starts to deposit. (b) The cathode potential needed to lower the Co2+ concentration to 1.00 x 10-5 M. (c) Based on (a) and (b) a

> Nickel is to be deposited on a platinum cathode (area = 120 cm2) from a solution that is 0.250 M in Ni2+ and buffered to a pH of 2.50. Oxygen is evolved at a partial pressure of 1.00 atm at a platinum anode with an area of 75 cm2. The cell has a resistan

> Copper is to be deposited from a solution that is 0.250 M in Cu(II) and is buffered to a pH of 4.00. Oxygen is evolved from the anode at a partial pressure of 730 torr. The cell has a resistance of 3.60 Ω, and the temperature is 25°C. Calculate (a) The t

> The cell Sn|Sn2+ (6.18 x 10-4 M) || Cd2+(5.95 x 10-2 M)|Cd has a resistance of 3.95 Ω. Calculate the initial potential that will be needed for a current of 0.062 A in this cell.

> Calculate the initial potential needed for a current of 0.065 A in the cell if this cell has a resistance of 4.50 Ω.

> Calculate the theoretical potential at 25°C needed to initiate the deposition of (a) Copper from a solution that is 0.250 M in Cu2+ and buffered to a pH of 3.00. Oxygen is evolved at the anode at 1.00 atm. (b) Tin from a solution that is 0.150

> Why is an auxiliary reagent always required in a coulometric titration?

> Why is the working electrode normally isolated from the counter electrode in a controlled-potential coulometric analysis?

> What is the purpose of a depolarizer?

> What is meant by Nernstian behavior in an indicator electrode?

> How do electro gravimetric and coulometric methods differ from potentiometric methods? Consider currents, voltages, and instrumentation in your answer.

> What is a supporting electrolyte, and what is its role in electrochemistry?

> Describe conditions that favor kinetic polarization in an electrochemical cell.

> How do concentration polarization and kinetic polarization resemble one another? How do they differ?

> Quinone can be reduced to hydroquinone with an excess of electrolytically generated Sn(II): The polarity of the working electrode is then reversed, and the excess Sn(II) is oxidized with Br2 generated in a coulometric titration: Sn2+ + Br2 ( Sn4+ + 2Br-