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All Textbook Solutions for Principles of Instrumental Analysis

19.1QAP 19.2QAP 19.3QAP 19.4QAP 19.5QAP A nucleus has a spin quantum number of 7/2. How many magnetic energy states does this nucleus have? What is the magnetic quantum number of each?19.7QAP 19.8QAP 19.9QAP Why is 133C-133C spin-spin splitting not observed in ordinary organic compounds?19.11QAP 19.12QAP 19.13QAP What is a rotating frame of reference?How will E for an isolated 13C nucleus compare with that of a 1H nucleus?19.16QAP 19.17QAP 19.18QAP 19.19QAP 19.20QAP 19.21QAP 19.22QAP 19.23QAP 19.24QAP 19.25QAP 19.26QAP 19.27QAP 19.28QAP 19.29QAP 19.30QAP The proton NMR spectrum in Figure 19.39 is for an organic compound containing a single atom of bromine. Identify the compound.The proton NMR spectrum in Figure 19-40 is for a compound having an empirical formula C4H7BrO2. Identify the compound.19.33QAP 19.34QAP 19.35QAP From the proton NMR spectrum in Figure 19-44, deduce the structure of this hydrocarbon From the proton spectrum given in Figure 19-45, determine the structure of this compound, a commc used painkiller; its empirical formula is C10H13NO2.19.38QAP 19.39QAP 19.40QAP 19.41QAP 19.42QAP 20.1QAP 20.2QAP 20.3QAP 20.4QAP 20.5QAP 20.6QAP 20.7QAP 20.8QAP 20.9QAP 20.10QAP 20.11QAP 20.12QAP 20.13QAP 20.14QAP 20.15QAP 20.16QAP 20.17QAP 20.18QAP 20.19QAP 21.1QAP 21.2QAP 21.3QAP 21.4QAP 21.5QAP 21.6QAP 21.7QAP 21.8QAP 21.9QAP 21.10QAP 21.11QAP 21.12QAP 21.13QAP 21.14QAP Calculate the electrode potentials of the following half-cells. (a) Ag+(0.0436 M)|Ag (b) Fe3+ (5.34 10-4M),Fe2+ (0.090 M)|Pt (c) AgBr(sat’d),Br- (0.037 M)|Ag 22.2QAP For each of the following half-cells, compare electrode potentials calculated from (1) concentration and (2) activity data. (a) HCI(0.0200 M),NaCI(0.0300 M)|H2(1.00 atm),Pt (b) Fe(CIO4)2(0.0111 M),Fe(CIO4)(0.0111 M)|Pt For each of the following half-cells, compare electrode potentials calculated from (I) concentration and (2) activity data. (a) Sn(ClO4)2(3.00 10-5 M),Sn(ClO4)4(6.00 10-5M)|Pt (b) Sn(ClO4)2(3.00 10-5 M),Sn(ClO4)4(6.00 10-5M),NaCIO4(0.0800 M)|Pt 22.5QAP Calculate the electrode potentials for the following systems: (a) Cr2O72-(5.00 10-3 M),Cr3+(2.50 10-2 M),H+ (0.100 M)|Pt (b) UO22+(0.100 M),U4+ (0.200 M),H+ (0.600 M)|Pt Calculate the theoretical potential of each of the following cells. Is the cell reaction spontaneous as written or spontaneous in the opposite direction? (a) Pt|Cr3+(2.00 10-4M),Cr2+(1.50 10-3 M)||Pb2+ (5.60 0215 10-2M)|Pb (b) Hg|Hg22+(2.00 10-2 M)||H+(1.50 10-2 M),V3+ (2.00 10-2M),VO2+(3.00 10-3M)|Pt (e) Pt|Fe3+(3.00 10-2 M), Fe2+ (4.00 10-5M)||Sn2+ (3.50 10-2M), Sn4+ (5.50 10-4 M)|Pt Calculate the theoretical potential of each of the following cells.Is the cell reaction spontaneous as written or spontaneous in the opposite direction? (a) Bi|BiO+ (0.0300 M),H+ (0.100 M)||I- (0.100 M), AgI(sat’d)|Ag (b) Zn|Zn2+(5.75 10-4M)||Fe(CN)64-(530 10-2 M),Fe(CN)63-(6.75 10-2M)|Pt (c) Pt,H2O (0.200 atm)|HCI(8.25 10-4M), AgCI(sat’d)| Ag 22.9QAP 22.10QAP Calculate the standard potential for the half-reaction BiOCl(s)+2H++3eBi(s)+Cl+H2O given that Ksp for BiOCl has a value of 8.1 10-19.Calculate the standard potential for the half-reaction Al (C2O4)2- + 3e- Al(s ) + 2C2O42- if the formation constant for the complex is 1.3 1013.From the standard potentials Tl++eTl(s)E0=0.336V TlCl(s)+eTl(s)+ClE0=0.557V calculate the solubility product constant for TlCl.From the standard potentials Ag2SeO4(s)+2e2Ag(s)+SeO42-E0=0.355V Ag++2eAg(s)E0=0.799V calculate the solubility product constant for Ag2SeO4.22.15QAP 22.16QAP 22.17QAP 22.18QAP 23.1QAP 23.2QAP 23.3QAP 23.4QAP 23.5QAP 23.6QAP 23.7QAP 23.8QAP 23.9QAP List the advantages and disadvantages of a potentiometric titration relative to a direct potentiometric measurement.23.11QAP What arc the advantages of microfabricated ISEs? Describe typical applications of this type of sensor.23.13QAP 23.14QAP 23.15QAP The following cell was used for the determination of pCrO4: SCE||CrO42- (xM),Ag2CrO4(sat’d)|Ag Calculate pCrO4 if the cd potential is —0.313 V.The following cell was used to determine the pSO4 of a solution: SCE||SO42- (xM),Hg2SO4 (sat’d)|Hg Calculate the pSO4 if the potential was —0.474 V.The formation constant for the mercury(II) acetate complex is Hg2++ 2OAc- Hg(OAc)2(aq) Kf = 2.7 108 Calculate the standard potential for the half-reaction Hg(OAc)2(aq) + 2e- Hg(l) + 2OAc-23.19QAP The cell Ag|AgCl(sat’d)||H+(a = x)|glass electrode has a potential of —0.2094 V when the solution in the right-hand compartment is a buffer of pH 4.006. The following potentials are obtained when the buffer is replaced with unknowns: (a) —0.2806 V and (b) —0.2132 V. Calculate the pH and the hydrogen ion activity of each unknown. (c) Assuming anuncertainty of 0.001 Vin the junction potential, what is the range of hydrogen ion activities withinwhich the true value might be expected to lie?The following cell was found to have a potential of 0.124 V: Ag|AgCl(sat’d)||Cu2+ (3.25 10-3 M|mernbrane electrode for Cu2+ When the solution of known copper activity was replaced with an unknown solution, the potential was found to be 0.055 V. What was the pCu of this unknown solution? Neglect the junction potential.The following cell was found to have a potential of 1.007 V: SCE||X- (0.0200 M),CdX2(sat’d)|Cd Calculate the solubility product of CdX2, neglecting the junction potential.The following cell was found to have a potential of —0.492 V: Ag|AgCl(sat’d)||HA(0.200 M),NaA(0.300 M)|H2(1.00 atm),Pt Calculate the dissociation constant of HA, neglecting the junction potential.23.24QAP 23.25QAP 23.26QAP 23.27QAP 24.1QAP Calculate the minimum difference in standard electrode potentials needed to lower the concentration of the metal M1 to 2.00 10-4 M ¡n a solution that is 1.00 10-1 M in the less-reducible metal M2 where (a) M2 is univalent and M1 is divalent. (b) M2 and M1 are both divalent, (c) M2 is trivalent and M1 is univalent, (d) M2is divalent and M1 is univalent, (e) M2 is divalent and M1 ¡s trivalent.24.3QAP Halide ions can he deposited at a silver anode, the reaction being Ag(s) + X- AgX(s) +e- Suppose that a cell was formed by immersing a silver anode in an analyte solution that was 0.0250 M Cl-,Br-, and I -ions and connecting the half-cell to a saturated calomel cathode via a salt bridge. (a) Which halide would form first and at what potential? Is the cell galvanic or electrolytic? (b) Could I- and Br- be separated quantitatively? (Take 1.00 l0-5 M as the criterion for quantitative removal of an ion.) If a separation is feasible, what range of cell potential could he used? (c) Repeat part (b) for I- and Cl-. (d) Repeat part (b) for Br- and Cl-.What cathode potential (versus SCE) would be required to lower the total Hg(II) concentration of the following solutions to 1.00 10-6 M (assume reaction product in each case is elemental Hg): (a) an aqueous solution of Hg2+? (b) a solution with an equilibrium SCN- concentration of 0.100 M? Hg2+ + 2SCN- Hg(SCN)2(aq) = Kf = 1.8 107 c) a solution with an equilibrium Br- concentration of 0.100 M? HgBr42++ 2e- Hg(l) + 4Br- E0= 0.223 V Calculate the Lime required for a constant current of 0.800 A to deposit 0.250 g of (a) Co(II) as the clementon a cathode and (h) as Co3O4 on an anode. Assume 100% current efficiency for both cases.Calculate the time required for a constant current of 0.875 A to deposit 0.350 g of (a) Tl(III) as the element on a cathode, (b) Tl(I) as the Tl2O3 on an anode, and (c) Tl(I) as the element on a cathode.24.8QAP 24.9QAP A 0.0712-g sample of a purified organic acid was dissolved in an alcohol-water mixture and titrated with coulometrically generated hydroxide ions. With a current of 0.0392 A, 241 s was required to reach aphenolphthalein end point. Calculate the equivalent mass of the acid.24.11QAP 24.12QAP Sulfide ion (S2- ) is formed in wastewater by the action of an aerobic bacteria on organic matter. Sulfide can be readily protonated to form volatile, toxic H2S. In addition to the toxicity and noxious odor, sulfide and H2S cause corrosion problems because they can be easily converted to sulfuric acid when conditions change to aerobic. One common method to determine sulfide is by coulometric titration with generated silver ion.At the generator electrode, the reaction is Ag Ag+ + e-. The titration reaction is S2- + 2Ag+ Ag2S(s). (a) A digital chloridometer was used to determine the mass of sulfide in a wastewater sample. The chloridometer reads out directly in ng Cl-.In chloride determinations, the same generator reaction is used,but the titration reaction is Cl- + Ag+ AgCI(s). Derive an equation that relates the desired quantity, mass S2- (ng), to the chloridometer readout in mass Cl- (ng). (b) A particular wastewater standard gave a reading of 1689.6 ng Cl-. What total charge in coulombs was required to generate the Ag+ needed to precipitate the sulfide in this standard? (c) The following results were obtained on 20.00-mL samples containing known amounts of sulfide.17 Each standard was analyzed in triplicate and the mass of chloride recorded. Convert each of the chloride results to mass S2- (ng). (d) Determine the average mass of S2- (ng), the standard deviation, and the %RSD) of each standard. (e) Prepare a plot ofthe average mass of S2- determined (ng) versus the actual mass (ng). Determine theslope, the intercept, the standard error, and the R2 value. Comment on the fit of the data to a linear model. (f) Determine the detection limit (ng) and in parts per million using a k factor of 2 (see Equation 1-12). (g) An unknown wastewater sample gave an average reading of 893.2 ng Cl. What is the mass of sulfide (ng)? If 20.00 mL of the wastewater sample was introduced into the titration vessel, what is the concentration of S2- n parts per million?25.1QAP 25.2QAP 25.3QAP 25.4QAP 25.5QAP 25.6QAP 25.7QAP 25.8QAP 25.9QAP 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 half-wave Potential (versus SCE) for the reduction of hydroquinone at an RDE from a solution buffered to a pH of 8.0. (b) Repeat the calculation in (a) for a solution buffered to a pH of 5.0.25.11QAP 25.12QAP 25.13QAP 25.14QAP 25.15QAP 25.16QAP 25.17QAP 26.1QAP 26.2QAP 26.3QAP 26.4QAP 26.5QAP 26.6QAP 26.7QAP 26.8QAP 26.9QAP 26.10QAP 26.11QAP 26.12QAP 26.13QAP 26.14QAP 26.15QAP 26.16QAP From the data in Problem 26-14, calculate for species C and D) (a) the resolution. (b) the length of column necessary to separate the two species with a resolution of 2.5.26.18QAP 26.19QAP 26.20QAP 26.21QAP 26.22QAP 26.23QAP 27.1QAP 27.2QAP 27.3QAP 27.4QAP 27.5QAP 27.6QAP 27.7QAP 27.8QAP 27.9QAP What are hyphenated GC methods? Briefly describe two hyphenated methods.27.11QAP 27.12QAP 27.13QAP 27.14QAP 27.15QAP 27.16QAP 27.17QAP 27.18QAP 27.19QAP The same polar compound is gas chromatographed on an SE-30 (very nonpolar) column and then on a Carbowax 20M (very polar column). I low will K=cS/cM vary between the two columns?27.21QAP 27.22QAP 27.23QAP 27.24QAP 27.25QAP 27.26QAP 27.27QAP 27.28QAP Why is GSC not used nearly as extensively as GLC?27.30QAP 28.1QAP 28.2QAP 28.3QAP How can the selectivity factor be manipulated in (a) GC and (b) LC?28.5QAP 28.6QAP 28.7QAP 28.8QAP 28.9QAP 28.10QAP 28.11QAP 28.12QAP 28.13QAP 28.14QAP 28.15QAP 28.16QAP Mass spectrometry is an extremely versatile detection system for GC. However, interfacing an HPLC system to a mass spectrometer is a much more difficult task. Describe the major reasons why it is more difficult to combine HPLC with mass spectrometry than it is to combine GC with mass spectrometry.28.18QAP 28.19QAP Two components in an HPLC separation have retention times that differ by 15 s. The first peak elutes in 9.0 min and the peak widths arc approximately equal. The dead time tM was 65 s. Use a spreadsheet to find the minimal number of theoretical plates needed to achieve the following resolution RS values: 0.50, 0.75, 0.90, 1.0, 1.10, 1.25, 1.50, 1.75, 2.0, 2.5. How would the results change if peak 2 were twice as broad as peak 1?28.21QAP 28.22QAP 28.23QAP 29.1QAP 29.2QAP 29.3QAP 29.4QAP 29.5QAP 29.6QAP 29.7QAP 29.8QAP 29.9QAP 29.10QAP 29.11QAP 30.1QAP 30.2QAP 30.3QAP 30.4QAP 30.5QAP 30.6QAP 30.7QAP 30.8QAP 30.9QAP 30.10QAP 30.11QAP 30.12QAP 31.1QAP A 0.5927-g sample was dissolved, and the Ca2+ and Ba2+ ions present were precipitated as BaC2O4· H20and CaC2O4 · H2O. The oxalates were then heated in a thermogravimetric apparatus leaving a residue that weighed 0.5127 g in the range of 320°C400°C and 0.4362 g in the range of 580°C-620°C. Calculate the percentage Ca and percentage Ba in the sample.31.3QAP 31.4QAP 31.5QAP 31.6QAP 31.7QAP 31.8QAP Why are the applications of TGA more limited than those for DSC?31.10QAP Describe the difference between power-compensated, heat-flux, and modulated DSC instruments.Identify X in each of the following nuclear reactions: (a) Z3068n+n01N2865i+X (b) P1530S1430i+X (c) P82214bB83214i+X (d) U92235+n014(n01)+Z3072n+X (e) T52130e+H12I53131+X (f) C2964u+XN2864i 32.2QAP 32.3QAP 32.4QAP 32.5QAP 32.6QAP 32.7QAP 32.8QAP 32.9QAP 32.10QAP 32.11QAP 32.12QAP 32.13QAP 32.14QAP 32.15QAP 32.16QAP 32.17QAP The streptomycin in 500 g of a broth was determined by addition of 1.25 mg of the pure antibiotic containing 14C. The specific activity of this preparation was found to be 240 cpm/mg for a 30-min count. From the mixture, 0.112 mg of purified streptomycin was isolated which produced 675 counts in 60.0 min. Calculate the concentration in parts per million streptomycin in the sample.Show, via a calculation, that the average kinetic energy of a population of thermal neutrons is approximately 0.04 eV 32.20QAP 32.21QAP 33.1QAP 33.2QAP 33.3QAP 33.4QAP Give the advantages and disadvantages of sequential injection analyzers compared to traditional flow Injection analyzers.33.6QAP Sketch a flow injection apparatus for the determination of sodium sulfite in aqueous samples.33.8QAP 34.1QAP 34.2QAP What quantities are used to describe particle size?34.4QAP 34.5QAP 34.6QAP 34.7QAP 34.8QAP 34.9QAP 34.10QAP 34.11QAP

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