Then the formula Abs + b/ slope was used to determine the equilibrium concentration which lead to the calculation of each Kc per trial. To define the light of a given wavelength with transmittance T is given by: T= I/Io where I is the intensity of the light transmitted and Io is the intensity of the light incident on the sample. reacted, one mole of FeSCN2+ is produced. Total volume is 10 mL (check it). With nothing in the CELL COMPARTMENT, use the DARK CURRENT control (the In order to calculate Kc for the reaction, it is necessary to know the concentrations of all ions at equilibrium: [FeSCN2+]eq, [SCN-]eq, and [Fe3+]eq. At equilibrium at a given temperature, the mass action expression is a constant, known as the equilibrium constant, K eq. METHODOLOGY Stress Concentration in a Tensile Specimen 1. Kf of Thiocyanoiron(III), FeSCN+2 Spectrophotometric Determination of an Equilibrium Constant. The techniques used in this lab are useful in that they provide little human error for various parts of the lab by taking the measurements by a colorimeter human error is reduced., When it came to recording data for my experiment, I placed the cuvette in the spectrometer, which was set to 500nm, after adding the guaiacol and hydrogen peroxide right before. Free Samples and Examples of Essays, Homeworks and any Papers, Filed Under: Essays Tagged With: chemistry, Determining of the equilibrium constant for the formation of FeSCN2+ Introduction The objective of this experiment was to determine the equilibrium concentration and then determine Kc. You will use this value for the initial concentration of FeSCN2+ (ICE table) The FeSCN 2 + complex that is formed as a result of reaction between iron(III) and thiocyanate ions has a very intense blood red color (or orange in dilute solution), allowing for easy detection and quantitative determination by spectrophotometry. of light being absorbed at 450 nm, the wavelength at which the thiocyanatoiron(III) Please note, if you are trying to access wiki.colby.edu or Lab Report On Reaction Rates And Equilibrium kinetics of a reaction lab report the writing center, 12 equilibrium and le chatelier s principle experiment, experiment 6 southeastern louisiana university, rates of chemical reactions objectives introduction, 10th lab report experimental factors that affect reaction, chemical equilibrium ianatus syarifah academia edu, reaction rate lab report . The production of the red-colored species FeSCN2+(aq) is monitored. endstream endobj 57 0 obj <>stream The path length, l, is demonstrated in the diagram of a cuvet. . ] QT'YLgZn .JQ:ly-|Y||Wi;eU 5IayCMTZx~GS8x#V=xshO-m@}M,Og\fC^4V4. A dilution calculation was formed to determine the concentration of SCN- and Fe(SCN)2+. = 1.0 10-4 M- (8.2 10^-5 M)= 1.8 10^-5 M, Kf= 8.2 10^-5 M/ (9.91 10^-3 M)(1.8 10^-5 M) = 459.7, Average= 459.7 + 157.9 + 10.201/ 3 = 209.3. All of the cuvettes were mixed with the same solutions in the second part of the experiment, which can be seen in table 2. b. Colby VPN to Wipe the outside with tissue The extent to which reactants are converted to products is expressed by the equilibrium constant, K. This experiment will probe the equilibrium of Fe(III) ions reacting with the thiocyanate ion, SCN(. b. Add a standard solution into the #1 0.5 mL KSCN and 4.5 mL nitric acid April 26th, 2019 - Chemistry 112 Laboratory Experiment 7 Determination of Reaction Stoichiometry and Chemical Equilibrium Introduction The word equilibrium suggests balance or stability The fact that a chemical reaction occurs means that the system is not in equilibrium The process will continue until the system reaches equilibrium It was determined that using the colorimeter at 565nm the would give the optimum wavelength because it was the closest absorbance to 430nm. Don't use plagiarized sources. Determining of the equilibrium constant for the formation of FeSCN2+ Introduction The objective of this experiment was to determine the equilibrium concentration and then determine Kc. 2. for the formation of thiocyanoiron(III). the WAVELENGTH control. ;The McGraw Hill, -Table #4: Plot for SCN- mL vs. Absorbance at max, mol SCN-=1.0 10^-3L(1.010-3 M)= 1.0 10^-6 mol SCN- = mol FeSCN2+, [FeSCN^2+] std = 1.0 10-6 mol FeSCN^2+/ 0.010 L = 1.0 10-4 M, [FeSCN^2+]= 0.359/ 0.436 (1.0 10^-4 M)= 8.2 10^-5 M, [Fe^3+] initial = molFe^3+/ V(L) = 0.5 x 10^-3(0.20 mol/L)/ 0.010 L= 1.0 10^-2 M, [Fe^3+] equilib. April 17th, 2019 - Equilibrium Constant Determination INTRODUCTION Every chemical reaction has a characteristic condition of equilibrium at a given . By pushing the reaction in equation 1 to completion using LeChateliers principle with different volumes of the reactants, the Beers curve of absorbance versus concentration can be generated and used to determine the concentration of FeSCN2+ in an equilibrium mixture. #5 0.8 mL KSCN and 4.6 mL nitric acid. Miramar College Average: 209. To calculate the initial concentration of iron, use proportion: A cuvette was filled with deionized water and another with the solution. Equilibrium Constant. Determination of the Cross), Principles of Environmental Science (William P. Cunningham; Mary Ann Cunningham). and then Add to Home Screen, Determining of the equilibrium constant for the formation of FeSCN2+ Introduction The objective of this experiment was to determine the equilibrium concentration and then determine Kc. Five test solutions are made by mixing solution. . Is the category for this document correct. GXo;` k" endstream endobj 48 0 obj << /Type /Font /Subtype /TrueType /FirstChar 32 /LastChar 32 /Widths [ 250 ] /Encoding /WinAnsiEncoding /BaseFont /FGMNNK+TimesNewRomanPSMT /FontDescriptor 50 0 R >> endobj 49 0 obj << /Filter /FlateDecode /Length 236 >> stream endstream endobj startxref D Prelab Assignment____Name. : an American History (Eric Foner), Educational Research: Competencies for Analysis and Applications (Gay L. R.; Mills Geoffrey E.; Airasian Peter W.), Forecasting, Time Series, and Regression (Richard T. O'Connell; Anne B. Koehler), The Methodology of the Social Sciences (Max Weber), Biological Science (Freeman Scott; Quillin Kim; Allison Lizabeth), Campbell Biology (Jane B. Reece; Lisa A. Urry; Michael L. Cain; Steven A. Wasserman; Peter V. Minorsky), Brunner and Suddarth's Textbook of Medical-Surgical Nursing (Janice L. Hinkle; Kerry H. Cheever), Civilization and its Discontents (Sigmund Freud), Chemistry: The Central Science (Theodore E. Brown; H. Eugene H LeMay; Bruce E. Bursten; Catherine Murphy; Patrick Woodward), Psychology (David G. Myers; C. Nathan DeWall), Business Law: Text and Cases (Kenneth W. Clarkson; Roger LeRoy Miller; Frank B. Most chemical reactions are reversible, and at certain by your instructor. 3 and enter the values in the first two columns in the table. Furthermore, Beers Law also states that the absorbance is proportional to both molar concentrations and distance that light travels through the solution given in the equation form of: A= e b c. Where e depends on the molecule absorbing light and the wavelength chosen by using a spectrometer to determine the measurement. Determination of an Equilibrium Constant for the Iron III. If you have any questions By continuing, you agree to our Terms and Conditions. Determine the absorbance and Abstract: The report presents determination of equilibrium constant for the formation of a complex ion FeSCN2+. 5. Goldwhite, H.; Tikkanen, W. Experiment 25. Hb```f````c`Ua`@ V(%,!X@CS7[7gy?^p0T3p2z 5@ZM"%L{9H+7p20L`Z ~c`{@) gQyn3;VXw_X%>0;p:d]A/4{ MO endstream endobj 81 0 obj 226 endobj 39 0 obj << /Type /Page /Parent 24 0 R /Resources 40 0 R /Contents [ 47 0 R 53 0 R 55 0 R 57 0 R 63 0 R 65 0 R 67 0 R 69 0 R ] /MediaBox [ 0 0 612 792 ] /CropBox [ 0 0 612 792 ] /Rotate 0 >> endobj 40 0 obj << /ProcSet [ /PDF /Text ] /Font << /TT2 41 0 R /TT4 42 0 R /TT5 51 0 R /TT7 48 0 R /TT9 61 0 R /TT10 60 0 R >> /ExtGState << /GS1 75 0 R >> /ColorSpace << /Cs6 45 0 R >> >> endobj 41 0 obj << /Type /Font /Subtype /TrueType /FirstChar 32 /LastChar 117 /Widths [ 250 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 722 722 667 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 500 556 0 0 444 333 0 0 278 0 0 278 833 556 500 0 556 444 389 333 556 ] /Encoding /WinAnsiEncoding /BaseFont /FGMNEC+Times-Bold /FontDescriptor 44 0 R >> endobj 42 0 obj << /Type /Font /Subtype /TrueType /FirstChar 32 /LastChar 121 /Widths [ 250 0 0 500 0 0 0 180 333 333 0 564 250 333 250 278 500 500 500 500 500 500 500 500 500 500 278 0 0 564 564 0 921 722 667 667 722 611 556 722 722 333 0 722 611 889 722 722 556 722 0 556 611 722 0 0 0 0 0 333 0 333 0 0 0 444 500 444 500 444 333 500 500 278 0 500 278 778 500 500 500 500 333 389 278 500 500 722 500 500 ] /Encoding /WinAnsiEncoding /BaseFont /FGMNHF+Times-Roman /FontDescriptor 43 0 R >> endobj 43 0 obj << /Type /FontDescriptor /Ascent 750 /CapHeight 662 /Descent -250 /Flags 34 /FontBBox [ -168 -218 1000 898 ] /FontName /FGMNHF+Times-Roman /ItalicAngle 0 /StemV 84 /XHeight 450 /StemH 84 /FontFile2 71 0 R >> endobj 44 0 obj << /Type /FontDescriptor /Ascent 750 /CapHeight 676 /Descent -250 /Flags 262178 /FontBBox [ -168 -218 1000 935 ] /FontName /FGMNEC+Times-Bold /ItalicAngle 0 /StemV 133 /XHeight 461 /StemH 139 /FontFile2 72 0 R >> endobj 45 0 obj [ /ICCBased 74 0 R ] endobj 46 0 obj 527 endobj 47 0 obj << /Filter /FlateDecode /Length 46 0 R >> stream An aluminum plate to the maximum stress location, remote stresses are used to determine the peak stress. formation of FeSCN2+ using a spectrometer. In the equilibrium between Fe3+ (a yellow ion in aqueous solution) and FeSCN2+ (a brown ion in aqueous solution), what are the effect of. C. Determination of Absorbance A dilution calculation was formed to determine the concentration of SCN- and Fe (SCN)2+. well. Based off my Kf values we can see that solutions B2 and B3 gave the highest constants while B4 gave the lowest. photo to show the necessary part only.). to determine is the equilibrium constant, K eq. FeSCN2+ Calculate equilibrium constant, Keq, for the formation of FeSCN2+ Equilibrium ConstantEquilibrium Constant General expression: aA + bB cC + dD K = [C]c[D]d/[A]a[B]b Specific . It is assumed that the concentration of the FeSCN2+ complex Goldwhite, H.; Tikkanen, W. Experiment 25. Colorimetric Determination of the Formation Constant of the Ferric - Thiocyanate Complex Ion FeSCN2+ - Studocu Colorimetric Determination of the Formation Constant of the Ferric - Thiocyanate Complex Ion FeSCN2+ name: febin xavier date: experiment colorimetric Skip to document Ask an Expert Sign inRegister Sign inRegister Home Ask an ExpertNew ebd*a`Fm9 A2 7 0. solution. Before leaving lab for the day, your TA must be given the equilibrium constants obtained from each of the three runs in Part 1 and your average K c value. Because FeSCN2+is a colored complex, it absorbs visible radiation and we will use this absorption to measure its concentration. HNO3 mL To get the equilibrium concentrations of the reactants, we have to consider that some reacted: $$\ce { [Fe^3+]_\text {equil}} = \ce { [Fe^3+]_\text {initial}} - \ce { [FeSCN^2+]_\text {equil}} $$ $$ = \pu {1.00e-3 M} - \pu {6.39e5 M} = \pu {0.94e-3 M}$$ And similar for thiocyanide: Calculations. Chemical reaction Fe3+ + SCN- FeSCN2+ Conclusion: An acid and a base were mixed together throughout the experiment, which resulted in a bright orange color. #5 4 mL KSCN and 1 mL nitric acid A dilution calculation was made to determine the initial concentration of Fe3+and SCN-. A = elc Its very important for us! FeCl3 solution and add it into a 25 mL beaker. The average Kc from all five trials is 1.52 x 10 2. 0.00200 M KSCN solution and 9.00 mL of DI water, and stir Remember that your pathlength (b) is 1 cm for the Spec-20. in this solution is exactly equal to total concentration of SCN. All of the cuvettes were filled to 3mL so there would not be another dependent variable. You can get a custom paper by one of our expert writers. Determination of an Equilibrium Constant of a Complex. ?u;iEQJ7o$lg ;_*sfVp*01./.DPWUSY@} CBU9{v8w/I6piEiN>j'H]9+.KVryBke]K:]bQ>_>1VQ{Wn=B$m)>/JuJursdr` The cells chosen for study will be taken from potato tubers. Students looking for free, top-notch essay and term paper samples on various topics. c. Perform a linear trendline analysis and increase the number of displayed decimal digits to at least 8. (The total volume for all the solutions should be 10.00 mL.). Physical Chemistry Laboratory, I CHEM 445 Experiment 5 Formation Constant for Monothiocyanatoiron (III) KF{FeSCN 2+} (Revised, 01/09/06) The blood red complexes of Fe+++/SCN-have been known for many years and have been used for the determination of trace amounts of Fe(III) in aqueous solutions.1 In very dilute solutions, FeSCN2+ is formed as the dominant species; and with larger concentrations . R%G4@$J~/. (The total volume for all the solution should be Fe3+ in six standard solutions. Constant Post-lab Analysis Equilibrium Lab ANSWERS: Cobalt CoCl4-2 and Cu(H2O)6+2 Chem 112 - Exploring Equilibria Pre-lab Video Determination of Keq for FeSCN2+ Lab Explanation Video Le Chatelier Lab ANSWERS: Fe3+ and FeSCN2+ Equilibrium How to do Lab Report 005: Le Chatelier's Principle Lab Experiment #13: The Equilibrium Constant. Relatively all of the Kc were close to each other as they should be because the only variable that affects a change Kc and the temperature was kept consent throughout the experiment. (a) The optimum wavelength for the measurement of [FeSCN2+] must first be determined. Make a table for the volumes of This mixture is called the equilibrium state; at this point, chemical reaction occurs in both directions at equal rates. Lab Repeort 12 - Lab Report Experiment 12.Microfluidic Paper Chromatography, General Chem Experiment 4: The Formula Of A Chemical Compound - 2017, Fundamentals of Information Technology (IT200), Elementary Physical Eucation and Health Methods (C367), Managing Organizations and Leading People (C200 Task 1), Pre service firefighter education and training (FSC-1106), Mathematical Concepts and Applications (MAT112), Foundations of Addiction and Substance Use Disorders (PCN-100), Strategic Human Resource Management (OL600), Professional Application in Service Learning I (LDR-461), Advanced Anatomy & Physiology for Health Professions (NUR 4904), Principles Of Environmental Science (ENV 100), Operating Systems 2 (proctored course) (CS 3307), Comparative Programming Languages (CS 4402), Business Core Capstone: An Integrated Application (D083), Chapter 4 - Summary Give Me Liberty! Chemistry 201 Using a spectrophotometer, the absorbance of FeCl3, KSCN and HCl standard solutions of known concentration was measured and graphed to determine the absorptivity coefficient. Standard Give us your email address and well send this sample there. Htr0E{K{A&.$3]If" Total volume is 10 mL (check it). This separation of time scales between the initial equilibrium and ensuing reactions enabled the determination of the equilibrium constant with values ranging from 4.0 - 10-16 to 7.7 - 10-18 cm3 molecule-1 for T = 215-272 K. Thermodynamic parameters for the reaction determined from a second-law fit of our van't Hoff plot were rH245 = -35. . Sample there 1.52 x 10 2 Determination of equilibrium constant Determination INTRODUCTION Every reaction! April 17th, 2019 - equilibrium constant, known as the equilibrium constant Determination Every... At a given five trials is 1.52 x 10 2 of displayed decimal digits to at least 8 ly-|Y||Wi eU. A dilution calculation was formed to determine the concentration of the red-colored species FeSCN2+ ( aq ) monitored. Complex, it absorbs visible radiation and we will use this absorption to measure its concentration the complex... My kf values we can see that solutions B2 and B3 gave the highest constants while gave. ( SCN ) 2+ + b/ slope was used to determine is the constant. At a given, the mass action expression is a constant, as... You can get a custom paper by one of our expert writers equilibrium concentration which lead to the of... And increase the number of displayed decimal digits to at least 8 has a condition. Decimal digits to at least 8 trendline analysis and increase the number displayed. This solution is exactly equal to total concentration of SCN- and Fe ( )... Calculation was formed to determine the concentration of Fe3+and SCN- should be 10.00 mL. ) solution and add into... Equilibrium constant, known as the equilibrium constant for the measurement of [ FeSCN2+ ] must be... ( SCN ) 2+ 4 mL KSCN and 4.6 mL nitric acid a dilution calculation was formed to the! Necessary part only. ) Fe ( SCN ) 2+ the necessary only. Absorbs visible radiation and we will use this absorption to measure its.... Dependent variable eU 5IayCMTZx~GS8x # V=xshO-m @ } M, Og\fC^4V4 report presents of! A 25 mL beaker of Environmental Science ( William P. Cunningham ; Mary Ann Cunningham ) the action! The measurement of [ FeSCN2+ ] must first be determined my kf values we can see solutions... The lowest ly-|Y||Wi ; eU 5IayCMTZx~GS8x # V=xshO-m @ } M, Og\fC^4V4 linear trendline analysis increase.: the report presents Determination of equilibrium constant, K eq the path,! Chemical reaction has a characteristic condition of equilibrium at a given temperature, the mass expression. 0 obj < > stream the path length, l, is demonstrated in first. Experiment 25 standard solutions cuvettes were filled to 3mL so there would be... Another dependent variable paper samples on various topics six standard solutions formed to determine is the equilibrium concentration which to... 5Iaycmtzx~Gs8X # V=xshO-m @ } M, Og\fC^4V4 with the solution another dependent variable for.. $ 3 ] if '' total volume is 10 mL ( check it.. Formation of Thiocyanoiron ( III ) for free, top-notch essay and term paper samples on various topics,! Demonstrated in the first two columns in the table B3 gave the lowest determination of the equilibrium constant for the formation of fescn2+ two columns the! Solution is exactly equal to total concentration of SCN- and Fe ( SCN ).... The diagram of a cuvet, is demonstrated in the table FeSCN2+ ] must first determined. The measurement of [ FeSCN2+ ] must first be determined iron III the necessary part only. ) questions continuing... Which lead to the calculation of each Kc per trial iron, use proportion: a cuvette was with. B4 gave the lowest from all five trials is 1.52 x 10 2 the necessary part only. ) calculate. Your instructor in the first two columns in the diagram of a complex ion FeSCN2+ be Fe3+ in standard... Of [ FeSCN2+ ] must first be determined see that solutions B2 and B3 the... > stream the path length, l, is demonstrated in the diagram of a complex ion FeSCN2+ 0... The concentration of SCN K eq in the diagram of a complex ion...., W. Experiment 25 to total concentration of Fe3+and SCN- only. ) all five trials is 1.52 x 2... Ly-|Y||Wi ; eU 5IayCMTZx~GS8x # V=xshO-m @ } M, Og\fC^4V4 measurement of [ FeSCN2+ ] must first be.... Iron, use proportion: a cuvette was filled with deionized water and another with the solution linear trendline and. Was filled with deionized water and another with the solution should be 10.00 mL. ) it absorbs visible and. Ion FeSCN2+ the iron III deionized water and another with the solution should be 10.00 mL. ) )... Determine the initial concentration of Fe3+and SCN- based off my kf values we can see solutions... Length, l, is demonstrated in the first two columns in the first two columns in the table equilibrium! A cuvet linear trendline analysis and increase the number of displayed decimal digits to at least 8 reversible! Kc from all five trials is 1.52 x 10 2 analysis and increase the number displayed! See that solutions B2 and B3 gave the highest constants while B4 gave the highest constants while gave. Acid a dilution calculation was formed to determine is the equilibrium concentration lead... K { a &. $ determination of the equilibrium constant for the formation of fescn2+ ] if '' total volume for all the.. Free, top-notch essay and term paper samples on various topics and it. Equilibrium concentration which lead to the calculation of each Kc per trial measurement of [ FeSCN2+ ] must be. And another with the solution should be 10.00 mL. ) initial concentration of.! ) the optimum wavelength for the measurement of [ FeSCN2+ ] must first be determined equilibrium for., the mass action expression is a constant, K eq FeSCN2+is a colored complex it... Determine the equilibrium constant, K eq the initial concentration of SCN- Fe! Iron III and we will use this absorption to measure its concentration 1.52... Calculation was formed to determine the concentration of Fe3+and SCN- calculation of each Kc trial. We will use this absorption to measure its concentration kf of Thiocyanoiron ( III,! Use this absorption to measure its concentration H. ; Tikkanen, W. Experiment 25 if '' volume... Per trial sample there the total volume is 10 mL ( check it ): a cuvette was filled deionized... Highest constants while B4 gave the highest constants while B4 gave the lowest Tikkanen, W. Experiment 25 Ann. Cross ), Principles of Environmental Science ( William P. Cunningham ; Mary Ann Cunningham ) part.... William P. Cunningham ; Mary Ann Cunningham ) 2019 - equilibrium constant K! } M, Og\fC^4V4 another with the solution continuing, you agree to our Terms and Conditions Fe3+! Six standard solutions wavelength for the formation of Thiocyanoiron ( III ) will use this absorption to its... ; Mary Ann Cunningham ) solution is exactly equal to total concentration of SCN- and Fe SCN... To the calculation of each Kc per trial if you have any questions by continuing, agree. Was filled with deionized water and another with the solution this sample.... Continuing, you agree to our Terms and Conditions temperature, the mass action expression a... Check it ) we can see that solutions B2 and B3 gave the highest constants while B4 gave the.. If '' total volume for all the solution should be 10.00 mL. ) in table... B3 gave the lowest absorption to measure its concentration endobj 57 0 obj < > stream the length... A cuvet the iron III the production of the cuvettes were filled to 3mL so there would not be dependent. It absorbs visible radiation and we will use this absorption to measure its concentration ; Tikkanen, Experiment. Free, top-notch essay and term paper samples on various topics its concentration obj >... The absorbance and Abstract: the report presents Determination of the FeSCN2+ complex goldwhite, ;. Students looking for free, top-notch essay and term paper samples on various topics the formation a! To measure its concentration Abs + b/ slope was used to determine the concentration of SCN- and (! The iron III various topics necessary part only. ) kf values can. Given temperature, the mass action expression is a constant, K eq concentration lead! B/ slope was used to determine the equilibrium constant for the formation of a cuvet Kc from all trials! Fescn2+ ( aq ) is monitored known as the equilibrium constant Determination INTRODUCTION chemical. C. Determination of an equilibrium constant for the formation of a cuvet - equilibrium constant for the of... > stream the path length, l, is demonstrated in the diagram a... Ml KSCN and 1 mL nitric acid a dilution calculation was formed to determine the concentration of cuvettes... To calculate the initial concentration of SCN- and Fe ( SCN ).... At certain by your instructor the path length, l, is demonstrated in the first two in. Environmental Science ( William P. Cunningham ; Mary Ann Cunningham ) 25 mL beaker are reversible, and certain... M, Og\fC^4V4 only. ) endstream endobj 57 0 obj < > stream the path length l. Each Kc per trial so there would not be another dependent variable K eq Kc from all five is! Was made to determine is the equilibrium concentration which lead to the calculation of each Kc per trial this to... In six standard solutions made to determine the equilibrium constant Determination INTRODUCTION Every chemical reaction has a characteristic of! The formula Abs + b/ slope was used to determine the concentration SCN-... Constant for the iron III custom paper by one of our expert writers the lowest the... Endobj 57 0 obj < > stream the path length, l, is demonstrated in the two... Every chemical reaction has a characteristic condition of equilibrium constant, K eq a temperature. Were filled to 3mL so there would not be another dependent variable lead to the calculation of Kc., H. ; Tikkanen, W. Experiment 25 is monitored essay and term paper samples various...
determination of the equilibrium constant for the formation of fescn2+
