Questions and Answers of Fundamentals Of Analytical Chemistry

Construct a coulometric titration curve of 100.0 mL of a 1 M H2SO4 solution containing Fe(II) titrated with Ce(IV) generated from 0.075 M Ce(III). The titration is monitored by potentiometry. The
Define(a) Voltammograms.(b) Hydrodynamic voltammetry.(c) Nernst diffusion layer.(d) Dropping mercury electrode.(e) Half-wave potential.(f) Limiting current.
Why is the reference electrode placed near the working electrode in a three-electrode cell?
Why is it necessary to buffer solutions in organic voltammetry?
Why are stripping methods more sensitive than other voltammetric procedures?
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
What is the purpose of the electrodeposition step in stripping analysis?
List the advantages and disadvantages of the hanging mercury drop electrode compared with platinum or carbon electrodes.
What is the relationship between(a) Absorbance and transmittance?(b) Concentration c and molar absorptivity e?
Identify factors that cause the Beer’s law relationship to be nonlinear.
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
A sophisticated ultraviolet/visible/near-IR instrument has a wavelength range of 189 to 2900 nm. What are its wavenumber and frequency ranges?
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 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.
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
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
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
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;
One common way to determine phosphorus in urine is to treat the sample after removing the protein with molybdenum (VI) and then reducing the resulting 12-molybdophosphate complex with ascorbic acid
Nitrite is commonly determined by a colorimetric procedure using a reaction called the Griess reaction. In this reaction, the sample containing nitrite is reacted with sulfanilimide and N-(1-Napthyl)
Define the term spectral bandpass of a monochromator.
Why does a hydrogen lamp produce a continuum rather than a line spectrum in the ultraviolet?
What are the differences between a photon detector and a thermal detector?
Describe the basic design difference between a spectrometer for emission measurements and one for absorption studies.
Describe how an absorption photometer and a fluorescence photometer differ from each other.
What is the difference between an absorption filter and an interference filter?
Define(a) Transducer.(b) Photocurrent.(c) n-type semiconductor.(d) Majority carrier.(e) Depletion layer.(f) Dynodes in a photomultiplier tube.
The indicator HIn has an acid dissociation constant of 4.80 x 10-6 at ordinary temperatures. The accompanying absorbance data are for 8.00 x 10-5 M solutions of the indicator measured in 1.00-cm
Solutions of P and Q individually obey Beer’s law over a large concentration range. Spectral data for these species in 1.00-cm cells are(a) Plot an absorption spectrum for a solution that is 6.45 x
A standard solution was put through appropriate dilutions to give the concentrations of iron shown in the accompanying table. The iron(II)-1,10,phenanthroline complex was then formed in 25.0-mL
The sodium salt of 2-quinizarinsulfonic acid (NaQ) forms a complex with Al3+ that absorbs strongly at 560 nm.19 The data collected on this system are shown in the accompanying table. (a) Find
The accompanying data were obtained in a slope-ratio investigation of the complex formed between Ni2+ and 1-cyclopentene-1-dithiocarboxylic acid (CDA). The measurements were made at 530 nm in 1.00-cm
The accompanying absorption data were recorded at 390 nm in 1.00-cm cells for a continuous-variations study of the colored product formed between Cd2+ and the complexing reagent R.(a) Find the
Mercury(II) forms a 1:1 complex with triphenyltetrazolium chloride (TTC) that exhibits an absorption maximum at 255 nm. The mercury(II) in a soil sample was extracted into an organic solvent
Predict the shape of photometric titration curves (after correction for volume change) if—at the wavelength selected—the molar absorptivities for the analyte A, the titrant T, and the product P
Why are fluorescence methods potentially more sensitive than absorption methods?
The reduced form of nicotinamide adenine dinucleotide (NADH) is an important and highly fluorescent coenzyme. It has an absorption maximum of 340 nm and an emission maximum at 465 nm. Standard
Why do some absorbing compounds show no fluorescence?
Why are phosphorescence lifetimes much longer than fluorescence lifetimes?
Why are fluorometers often more useful than spectrofluorometers for quantitative analysis?
The volumes of a 1.10 ppm standard solution of Zn2+ shown in the following table were pipetted into separatory funnels each containing 5.00 mL of an unknown zinc solution. Each was extracted with
Why are the lines from a hollow-cathode lamp generally narrower than the lines emitted by atoms in a flame?
In flame AA with a hydrogen/oxygen flame, the absorbance for calcium decreases in the presence of large concentrations of phosphate ion.(a) Suggest an explanation for this observation.(b) Suggest
Discuss the differences that result in ICP atomic emission when the plasma is viewed axially rather than radially.
A 5.00-mL sample of blood was treated with trichloroacetic acid to precipitate proteins. After centrifugation, the resulting solution was brought to pH 3 and extracted with two 5-mL portions of
The chromium in a series of steel samples was determined by ICP emission spectroscopy. The spectrometer was calibrated with a series of standards containing 0, 2.0, 4.0, 6.0, and 8.0 μg K2Cr2O7 per
Lead was determined in a brass sample by atomic absorption and the method of standard additions. The original sample was dissolved and diluted to 50.0 mL. This solution was introduced into an AA
What are the y-axis and the x-axis of an ordinary mass spectrum?
Why are detection limits for ICPMS often lower with double-focusing mass spectrometers than with quadrupole mass spectrometers?
Why are fragments often produced with electron ionization?
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?
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
What is the difference between a precursor ion and a product ion in tandem mass spectrometry?
Calculate the product concentrations versus time for a pseudo-first-order reaction with k9 5 0.015 s21 and 3A40 5 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
What is a collector ion, and how is it used?
What does the term salting out a protein mean? What is the salting in effect?
What two events accompany the separation process?
Name three methods based on mechanical phase separation.
How do strong- and weak-acid synthetic ion-exchange resins differ in structure?
What are the major differences between gas-liquid and liquid-liquid chromatography?
Describe a method for determining the number of plates in a column.
Describe two general methods for improving the resolution of two substances on a chromatographic column.
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
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?
To determine the equilibrium constant for the reaction25.0 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 following data are for a liquid chromatographic column:A chromatogram of a mixture of species A, B, C, and D provided the following data:Calculate(a) The number of plates from each peak.(b) The
Describe the preparation of exactly 1.00 L of 0.1000 M HCl from primary-standard-grade NaCl using a cation-exchange resin.
The following data were obtained by gas-liquid chromatography on a 40-cm packed column:Calculate(a) An average number of plates from the data.(b) The standard deviation for the average in (a).(c) An
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.
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
Explain how you would use one of the flow meters in Figure 30-2. FIGURE 30-2 Two different types of soap-bubble flow meter. Agilent Technologies
What kind of mixtures are separated by gas-solid chromatography?
What is meant by temperature programming in gas chromatography?
How do the following capillary columns differ?(a) PLOT columns (b) WCOT columns(c) SCOT columns
What properties should the stationary phase liquid for gas chromatography possess?
What are the advantages of fused-silica capillary columns compared with glass or metal columns?
What is the effect of stationary phase film thickness on gas chromatograms?
One method for quantitative determination of the concentration of constituents in a sample analyzed by gas chromatography is the area normalization method. In this method, complete elution of all the
A 0.7041-g sample of impure mercury(II) oxide was dissolved in an unmeasured excess of potassium iodide. Reaction:Calculate the percentage of HgO in the sample if titration of the liberated hydroxide
The benzoic acid extracted from 86.7 g of catsup required a 15.61-mL titration with 0.0654 M NaOH. Express the results of this analysis in terms of percent sodium benzoate (144.10 g/mol).
Suggest a range of sample masses for the indicated primary standard if it is desired to use between 35 and 45 mL of titrant:(a) 0.180 M HClO4 titrated against Na2CO3(CO2 product).(b) 0.102 M HCl
A 25.0-mL aliquot of vinegar was diluted to 250 mL in a volumetric flask. Titration of 50.0-mL aliquots of the diluted solution required an average of 25.23 mL of 0.09041 M NaOH. Express the acidity
(a) Compare the masses of potassium hydrogen phthalate (204.22 g/mol), potassium hydrogen iodate (389.91 g/mol), and benzoic acid (122.12 g/mol) needed for a 50.00-mL standardization of 0.0600 M
Calculate the molar concentration of a dilute HCl solution if(a) A 50.00-mL aliquot yielded 0. 6027 g of AgCl.(b) The titration of 25.00 mL of 0.04096 M Ba(OH)2 required 17.93 mL of the acid.(c) The
Standardization of a sodium hydroxide solution against potassium hydrogen phthalate (KHP) yielded the results in the following table.Calculate(a) The average molar concentration of the base.(b) The
If 1.000 L of 0.2000 M NaOH was unprotected from the air after standardization and absorbed 14.2 mmol of CO2, what is its new molar concentration when it is standardized against a standard solution
How would you prepare 500 mL of(a) 0.100 M H2SO4 from a reagent that has a density of 1.1539 g/mL and is 21.8% H2SO4 (w/w)?(b) 0.200 M NaOH from the solid?(c) 0.08000 M Na2CO3 from the pure solid?
What types of organic nitrogen-containing compounds tend to yield low results with the Kjeldahl method unless special precautions are taken?
Why is it common practice to boil the solution near the equivalence point in the standardization of Na2CO3 with acid?
Describe how Na2CO3 of primary-standard grade can be prepared from primary-standard NaHCO3.
Generate a curve for the titration of 50.00 mL of a solution in which the analytical concentration of HClO4 is 0.1000 M and that for formic acid is 0.0800 M. Calculate the pH after addition of 0.00,
Generate a curve for the titration of 50.00 mL of a solution in which the analytical concentration of NaOH is 0.1000 M and that for hydrazine is 0.0800 M. Calculate the pH after addition of 0.00,
Identify by letter the curve you would expect in the titration of a solution containing(a) Disodium maleate, Na2M, with standard acid.(b) Pyruvic acid, HP, with standard base.(c) Sodium carbonate,
How would you prepare 1.00 L of a buffer with a pH of 6.00 from 0.500 M Na3AsO4 and 0.400 M HCl?
This photo shows a buret that has at least two defects on the scale that were created during its fabrication.Answer the following questions about the buret, its origin, and its use.(a) Under what
What is the pH of the buffer formed by mixing 50.0 mL of 0.200 M NaH2PO4 with(a) 50.0 mL of 0.100 M HCl?(b) 50.0 mL of 0.100 M NaOH?
Identify the principal conjugate acid-base pair and calculate the ratio between them in a solution that is buffered to pH 6.00 and contains(a) H2SO3.(b) Citric acid.(c) Malonic acid.(d) Tartaric acid.
Calculate the pH of a solution that is(a) 0.0100 M in HClO4 and 0.0300 M in monochloroacetic acid.(b) 0.0100 M in HCl and 0.0150 M in H2SO4.(c) 0.0100 M in NaOH and 0.0300 M in Na2S.(d) 0.0100 M in
Calculate the pH of a solution that is(a) 0.0100 M in HCl and 0.0200 M in picric acid.(b) 0.0100 M in HCl and 0.0320 M in benzoic acid.(c) 0.0100 M in NaOH and 0.075 M in Na2CO3.(d) 0.0100 M in NaOH
Calculate the equilibrium concentration of undissociated HCOOH in a formic acid solution with an analytical formic acid concentration of 0.0750 and a pH of 3.500.

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