Question: The equilibrium constant for the reaction 2CrO42- +
The equilibrium constant for the reaction
2CrO42- + 2H+ ⇌ Cr2O72- + H2O
is 4.2 x 1014. The molar absorptivities for the two principal species in a solution of K2CrO7 are
Four solutions were prepared by dissolving 4.00 x 10-4, 3.00 x 10-4, 2.00 x 10-4, and 1.00 x 10-4 moles of K2Cr2O7 in water and diluting to 1.00 L with a pH 5.60 buffer. Calculate theoretical absorbance values (1.00-cm cells) for each solution, and plot the data for
(a) 345 nm,
(b) 370 nm, and
(c) 400 nm.
> Several buffer solutions were made 1.00 x 10-4M in the indicator of Problem 24-19. Absorbance data (1.00-cm cells) are Calculate the pH of each solution. Indicator of Problem 24-19: Indicator HIn
> What is the absorbance at 595 nm (1.00-cm cells) of a solution that is 1.25 × 10-4M in the indicator of Problem 24-19 and has a pH of a) 5.30, b) 5.70, c) 6.10? Indicator of Problem 24-19: The indicator HIn
> Calculate the absorbance (1.00-cm cells) at 450 nm of a solution in which the total molar concentration of the indicator described in Problem 24-19 is 8.00 × 10-5M and the pH is a) 4.92, b) 5.46, c) 5.93, d) 6.16.
> The indicator HIn has an acid dissociation constant of 4.80 × 10-6 at ordinary temperatures. The accompanying absorbance data are for 8.00 × 10-5 M solutions of the indicator measured in 1.00-cm cells in strongly acidic and stro
> Molar absorptivity data for the cobalt and nickel complexes with 2,3-quinoxalinedithiol are εCo = 36,400 and εNi = 5520 at 510 nm and εCo = 1240 and εNi = 17,500 at 656 nm. A 0.425-g sample was dissolved and diluted to 50.0 mL. A 25.0-mL aliquot was trea
> A. J. Mukhedkar and N. V. Deshpande (Anal. Chem., 1963, 35, 47, DOI: 10.1021/ac60194a014) report on a simultaneous determination for cobalt and nickel based on absorption by their 8-quinolinol complexes. Molar absorptivities (L mol-1 cm-1 ) are ï
> Iron(III) forms a complex with thiocyanate ion that has the formula Fe(SCN) 2+. The complex has an absorption maximum at 580 nm. A specimen of well water was assayed according to the following scheme. Calculate the concentration of iron in parts per mill
> A 5.24-g petroleum specimen was decomposed by wet ashing and subsequently diluted to 500 mL in a volumetric flask. Cobalt was determined by treating 25.00-mL aliquots of this diluted solution as follows: Assume that the Co(II)/ligand chelate obeys Beer&
> What is the “operational definition of pH”? Why is it used?
> The accompanying data (1.00-cm cells) were obtained for the spectrophotometric titration of 10.00 mL of Pd(II) with 2.44 × 10-4 M Nitroso R (O. W. Rollins and M. M. Oldham, Anal. Chem., 1971, 43, 262, DOI: 10.1021/ac60297a026): Calculate th
> Ethylenediaminetetraacetic acid displaces bismuth(III) from its thiourea complex: Bi(tu)63+ + H2Y2- → BiY- + 6tu + 2H+ where tu is the thiourea molecule, (NH2)2CS. Predict the shape of a photometric titration curve based on this process, given that the
> Iron(III) reacts with thiocyanate ion (SCN) to form the red complex, Fe(SCN)2+. Sketch a photometric titration curve for Fe(III) with thiocyanate ion when a photometer with a green filter is used to collect data. Why is a green filter used?
> Sketch a photometric titration curve for the titration of Sn2+ with MnO-4. What color radiation should be used for this titration? Explain.
> A portable photometer with a linear response to radiation registered 75.5 µA with a blank solution in the light path. Replacement of the blank with an absorbing solution yielded a response of 23.7 µA. Calculate (a) The percent transmittance of the sampl
> A photometer with a linear response to radiation gave a reading of 690 mV with a blank in the light path and 169 mV when the blank was replaced by an absorbing solution. Calculate a) The transmittance and absorbance of the absorbing solution. b) The ex
> The logarithm of the molar absorptivity of phenol in aqueous solution is 4.297 at 211 nm. Calculate the range of phenol concentrations that can be used if the absorbance is to be greater than 0.150 and less than 1.500 with a 1.25-cm cell.
> The logarithm of the molar absorptivity for acetone in ethanol is 2.75 at 366 nm. Calculate the range of acetone concentrations that can be used if the absorbance is to be greater than 0.100 and less than 2.000 with a 1.50-cm cell.
> The molar absorptivity for aqueous solutions of phenol at 211 nm is 5.28 × 103 L cm-1 mol-1. Calculate the permissible range of phenol concentrations if the transmittance is to be less than 85% and greater than 7% when the measurements are made in 1.00-c
> The molar absorptivity for the complex formed between bismuth (III) and thiourea is 9.32 × 103 L cm-1 mol-1 at 470 nm. Calculate the range of permissible concentrations for the complex if the absorbance is to be no less than 0.10 nor greater than 0.90 wh
> Give several advantages of a potentiometric titration over a direct potentiometric measurement.
> Define the term spectral bandpass of a monochromator.
> Describe the differences between the following pairs of terms, and list any particular advantages possessed by one over the other: (a) Solid-state photodiodes and phototubes as detectors for electromagnetic radiation. (b) Phototubes and photomultiplier
> The following data were taken from a diode-array spectrophotometer in an experiment to measure the spectrum of the Co (II)-EDTA complex. The column labeled Psolution is the relative signal obtained with sample solution in the cell after subtraction of th
> An interference filter is to be constructed for isolation of the CS2 absorption band at 4.54 µm. a) If the determination is to be based on first-order interference, how thick should the dielectric layer be (refractive index 1.54)? b) What other wavelen
> Define (a) Transducer. (b) Photocurrent. (c) N-type semiconductor. (d) Majority carrier. (e) Depletion layer. (f) Dynodes in a photomultiplier tube.
> What is the difference between an absorption filter and an interference filter?
> Describe how an absorption photometer and a fluorescence photometer differ from each other.
> Describe the basic design difference between a spectrometer for emission measurements and one for absorption studies.
> What are the differences between a photon detector and a thermal detector?
> Why does a hydrogen lamp produce a continuum rather than a line spectrum in the ultraviolet?
> How does information supplied by a direct potentiometric measurements of pH differ from that obtained from a potentiometric acid-base titration?
> A portable photometer with a linear response to radiation registered a photocurrent of 75.9 μA with a blank solution in the light path. Replacement of the blank with an absorbing solution yielded a response of 23.5 μA. Calculate a) The transmittance of t
> A photometer with a linear response to radiation gave a reading of 625 mV with a blank in the light path and 149 mV when the blank was replaced by an absorbing solution. Calculate a) The percent transmittance and absorbance of the absorbing solution. b)
> What are the major advantages of Fourier transform IR instruments over dispersive IR instruments?
> What non-instrumental variables must be controlled to assure reproducible absorbance data?
> What is the purpose of a) The 0% T adjustment b) The 100% T adjustment of a spectrophotometer?
> What minimum requirement is needed to obtain reproducible results with a single-beam spectrophotometer?
> The relationships described in Problems 23-7 and 23-8 may be of help in solving the following. a) Calculate the wavelength of maximum emission of a tungsten-filament bulb operated at 2870 K and at 3000 K. b) Calculate the total energy output of the bul
> Stefan’s law states that the total energy emitted by a blackbody per unit time and per unit area is Et = αT4 where α is 5.69 × 10-8W/m2 K4. Calculate the total energy output in W>m2 for the blackbodies described in Problem 23-7.
> The Wien displacement law states that the wavelength maximum in micrometers for blackbody radiation is (maxT = 2.90 × 103 Where T is the temperature in kelvins. Calculate the wavelength maximum for a blackbody that has been heated to a) 4000 K, b) 330
> Describe the differences between the following pairs of terms, and list any particular advantages of one over the other: (a) Spectrophotometers and photometers. (b) Spectrographs and spectrometers. (c) Monochromators and polychromators. (d) Single-beam
> What is the source of a) The asymmetry potential in a membrane electrode? b) The boundary potential in a membrane electrode? c) A junction potential in a glass/calomel electrode system? d) The potential of a crystalline-membrane electrode used to determi
> Why is iodine sometimes introduced into a tungsten lamp?
> Why are photomultiplier tubes unsuited for the detection of infrared radiation?
> Why do quantitative and qualitative analyses often require different monochromator slit widths?
> Describe the differences between “real” deviations from Beer’s law and those due to instrumental or chemical factors.
> Identify factors that cause the Beer’s law relationship to be nonlinear.
> What is the relationship between (a) Absorbance and transmittance? (b) Concentration c and molar absorptivity ε?
> In a solution of pH 5.3, the indicator bromocresol purple exhibits a yellow color, but when the pH is 6.0, the indicator solution changes to purple. Discuss why these colors are observed in terms of the wavelength regions and colors absorbed and transmit
> 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) ethylenediamine to form a colored species that absorbs
> 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 to give an intense blue-colored species called molybdenu
> How does a gas-sensing probe differ from other membrane electrodes?
> Briefly describe or define (a) Indicator electrode. (b) Reference electrode. (c) Electrode of the first kind. (d) Electrode of the second kind. Answers: a) Indicator electrode: An indicator electrode is an electrode used in potentiometry that responds
> Perform the indicated operations and reduce answers to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> Represent the compound fractions in Problem as simple fractions reduced to lowest terms.
> Represent the compound fractions in Problem as simple fractions reduced to lowest terms.
> imagine that the indicated “solutions” were given to you by a student whom you were tutoring in this class. (A) Is the solution correct? If the solution is incorrect, explain what is wrong and how it can be corrected.
> imagine that the indicated “solutions” were given to you by a student whom you were tutoring in this class. (A) Is the solution correct? If the solution is incorrect, explain what is wrong and how it can be corrected.
> imagine that the indicated “solutions” were given to you by a student whom you were tutoring in this class. (A) Is the solution correct? If the solution is incorrect, explain what is wrong and how it can be corrected.
> imagine that the indicated “solutions” were given to you by a student whom you were tutoring in this class. (A) Is the solution correct? If the solution is incorrect, explain what is wrong and how it can be corrected.
> perform the indicated operations and reduce answers to lowest terms. Represent any compound fractions as simple fractions reduced to lowest terms.
> perform the indicated operations and reduce answers to lowest terms. Represent any compound fractions as simple fractions reduced to lowest terms.
> factor out all factors common to all terms.
> perform the indicated operations and reduce answers to lowest terms. Represent any compound fractions as simple fractions reduced to lowest terms.
> perform the indicated operations and reduce answers to lowest terms. Represent any compound fractions as simple fractions reduced to lowest terms.
> perform the indicated operations and reduce answers to lowest terms. Represent any compound fractions as simple fractions reduced to lowest terms.
> perform the indicated operations and reduce answers to lowest terms. Represent any compound fractions as simple fractions reduced to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> refer to the following polynomials: Multiply (A) and (C).
> Perform the indicated operations and reduce answers to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> Perform the indicated operations and reduce answers to lowest terms.
> factor by grouping.
> factor out all factors common to all terms.
> factor out all factors common to all terms.
> discuss the validity of each statement. If the statement is true, explain why. If not, give a counterexample. If k is a positive integer, then u2k + 1 + v2k + 1 can be factored.
> discuss the validity of each statement. If the statement is true, explain why. If not, give a counterexample. If m and n are positive integers and m ≠ n, then um - vn is not factorable.
> factor completely. If a polynomial cannot be factored, say so.
> factor completely. If a polynomial cannot be factored, say so.
> indicate true (T) or false (F). 8. a + cb = a + bc 10. 12. 14. 16. 18 20 22. 24. 26.
> factor completely. If a polynomial cannot be factored, say so.
> factor completely. If a polynomial cannot be factored, say so.
> factor completely. If a polynomial cannot be factored, say so.
> factor completely. If a polynomial cannot be factored, say so.
> factor completely. If a polynomial cannot be factored, say so.
> factor completely. If a polynomial cannot be factored, say so.
> factor completely. If a polynomial cannot be factored, say so.
> Each ounce of food M contains 8 units of calcium, and each ounce of food N contains 5 units of calcium. A 160-ounce diet mix is formed using foods M and N. If x is the number of ounces of food M used, write an algebraic expression that represents the tot
> factor completely. If a polynomial cannot be factored, say so.
> Six thousand tickets are to be sold for a concert, some for $20 each and the rest for $35 each. If x is the number of $20 tickets sold, write an algebraic expression that represents the gross receipts from ticket sales, assuming all tickets are sold. Sim
> refer to the following polynomials: Subtract (A) from (B).
> factor completely. If a polynomial cannot be factored, say so.
> A person has $100,000 to invest. If $x are invested in a money market account yielding 7% and twice that amount in certificates of deposit yielding 9%, and if the rest is invested in high-grade bonds yielding 11%, write an algebraic expression that repre
> factor completely. If a polynomial cannot be factored, say so.
