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 the injection end of the capillary, how long does it take in minutes for the analyte cation to reach the detector after the field is applied?
> A packed column in gas chromatography had an inside diameter of 5.0 mm. The measured volumetric flow rate at the column outlet was 48.0 mL/min. If the column porosity was 0.43, what was the linear flow velocity in cm/s?
> An open tubular column used for gas chromatography had an inside diameter of 0.15 mm. A volumetric flow rate of 0.85 mL/min was used. Find the linear flow velocity in cm/s at the column outlet.
> An aqueous solution containing MgCl2 and HCl was analyzed by first titrating a 25.00-mL aliquot to a bromocresol green end point with 17.53 mL of 0.02932 M NaOH. A 10.00-mL aliquot was then diluted to 50.00 mL with distilled water and passed through a st
> Describe the preparation of exactly 1.00 L of 0.1000 M HCl from primary-standard-grade NaCl using a cation-exchange resin.
> The total cation content of natural water is often determined by exchanging the cations for hydrogen ions on a strong-acid ion-exchange resin. A 25.0-mL sample of a natural water was diluted to 100 mL with distilled water, and 2.0 g of a cation-exchange
> To determine the equilibrium constant for the reaction 25.0 mL of a 0.0100 M aqueous solution of I2 was extracted with 10.0 mL of CHCl3. After extraction, spectrophotometric measurements revealed that the I2 concentration of the aqueous layer was 1.12 x
> A 0.150 M aqueous solution of the weak organic acid HA was prepared from the pure compound, and three 50.0-mL aliquots were transferred to 100.0-mL volumetric flasks. Solution 1 was diluted to 100.0 mL with 1.0 M HClO4, solution 2 was diluted to the mark
> If 30.0 mL of water that is 0.0500 M in Q is to be extracted with four 10.0-mL portions of an immiscible organic solvent, what is the minimum distribution coefficient that allows transfer of all but the following percentages of the solute to the organic
> What is the minimum distribution coefficient that permits removal of 99% of a solute from 50.0 mL of water with a) Two 25.0-mL extractions with toluene? b) Five 10.0-mL extractions with toluene?
> What volume of n-hexane is required to decrease the concentration of Z in Problem 29-12 to 2.00 x 10-5 M if 40.0 mL of 0.0200 M Z is extracted with a) 50.0-mL portions of n-hexane? b) 25.0-mL portions? c) 10.0-mL portions?
> What are the y-axis and the x-axis of an ordinary mass spectrum?
> What volume of n-hexane is required to decrease the concentration of X in Problem 29-11 to 1.00 x 10-4 M if 25.0 mL of 0.0500 M X is extracted with a) 25.0-mL portions? b) 10.0-mL portions? c) 2.0-mL portions?
> The distribution coefficient for Z between n-hexane and water is 5.85. Calculate the percent of Z remaining in 25.0 mL of water that was originally 0.0550 M in Z after extraction with the following volumes of n-hexane: a) One 20.0-ml portion. b) Two 10
> The distribution constant for X between n-hexane and water is 8.9. Calculate the concentration of X remaining in the aqueous phase after 50.0 mL of 0.200 M X is treated by extraction with the following quantities of n-hexane: a) One 40.0-ml portion. b)
> Describe two general methods for improving the resolution of two substances on a chromatographic column.
> Describe a method for determining the number of plates in a column.
> What are the major differences between gas-liquid and liquid-liquid chromatography?
> Repeat the calculations in Problem 29-32 assuming KM = 5.81 and KN = 6.20. Data from Problem 29-32: From distribution studies, species M and N are known to have water/hexane distribution constants of 5.99 and 6.16 (K = [X]H2O/[X]hex), where X = M or N.
> From distribution studies, species M and N are known to have water/hexane distribution constants of 5.99 and 6.16 (K = [X]H2O/[X]hex), where X = M or N. The two species are to be separated by elution with hexane in a column packed with silica gel contain
> If VS and VM for the column in Problem 29-28 are 19.6 and 62.6 mL, respectively, and a nonretained air peak appears after 1.9 minutes, calculate a) The retention factor for each compound. b) The distribution constant for each compound. c) The selectiv
> List the variables that lead to band broadening in chromatography.
> What function does the ICP torch serve in mass spectrometry?
> List three advantages of kinetic methods. Can you think of two possible limitations of kinetic methods when compared to equilibrium methods?
> The analysis of a multicomponent mixture by kinetic methods is sometimes referred to as a “kinetic separation.” Explain the meaning of this term.
> Define the following terms as they are used in kinetic methods of analysis. (a) Order of a reaction (b) Pseudo-first-order (c) Enzyme (d) Activator (e) Michaelis constant (f) Differential method (g) Integral method (h) Predictive method
> Equation 28-19 can be rearranged to produce the equation where vmax = k2[E]0, the maximum velocity when [S] is large. a) Suggest a way to use this equation in the construction of a calibration (working) curve for the enzymatic determination of substrat
> Show mathematically that, for an enzyme reaction obeying Equation 28-19, the substrate concentration for which the rate equals vmax/2 is equal to Km. Equation 28-19:
> Find the relative error associated with the assumption that k’ is invariant during the course of a pseudo-first order reaction under the following conditions:
> Calculate the number of lifetimes t required for a pseudo-first-order reaction to achieve the levels of completion listed in Problem 28-8. Levels of completion listed in Problem 28-8: a) 10%. b) 90%. c) 99.9%. d) 50%. e) 99%. f) 99.99%.
> Find the number of half-lives required to reach the following levels of completion: a) 10%. b) 90%. c) 99.9%. d) 50%. e) 99%. f) 99.99%.
> Find the first-order rate constant for a reaction that is 75.0% complete in a) 0.0100 s. b) 0.400 s c) 1.00 s. d) 3299 s e) 26.8 s f) 9.38 ns.
> Find the natural lifetime in seconds for first-order reactions corresponding to a) k = 0.497s-1 . b) k = 5.35 h-1. c) [A]0 = 3.16 M, and [A]t = 0.496 M at t = 3876 s. d) [P]∞ = 0.255 M, and [P]t = 0.0566 M at t = 9.54 s (assume 1 mol of product is fo
> Name three characteristics of inductively coupled plasmas that make them suitable for atomic mass spectrometry.
> Derive an expression for the half-life of the reactant in a first-order process in terms of the rate constant k.
> Explain why pseudo-first-order conditions are utilized in many kinetic methods.
> 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?
> 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 typical simple infrared spectrophotometer covers a wavelength range from 3 to 15 µm. Express its range (a) In wavenumbers and (b) In hertz.
> 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
