the equilibrium concentration of [FeSCN2+]eq were calculated using the Keq Simulator. initial = 0.00020 M, and an equilibrium concentration, [FeSCN 2+] eq = 0.0000195 M, the ICE table will be: Fe3+ + SCN FeSCN2+ Initial 0.00100 0.00020 0 Change -0.0000195 -0.0000195 + 0.0000195 Equilibrium 0.00098 0.00018 0.0000195 The initial concentration of FeSCN2+ is zero because the reaction has not yet started, but at The equilibrium constant of this reaction was calculated to be 1563 which is The calculated R2 value for the line of best fit was 0.9894 (on a scale of 0 to 1), which means that there is a very strong, positive correlation between concentration (M) and absorbance, so therefore, the graph is highly accurate and the trendline, fits our observations. were done separately for all six samples of the data. and the Take Scan button was clicked. reduce fluctuations in the temperature. Simulator. low precision of data can be explained through systematic errors therefore differentiating the To gain more practice diluting stock solutions. endobj Equilibrium constant is directly dependent on temperature, therefore if the temperature was not By plotting the Table 6: Equilibrium Constant values of the standard solutions' Unknown Keq concentration vs. its respective absorbance 1 384.3118 and applying . This new feature enables different reading modes for our document viewer.By default we've enabled the "Distraction-Free" mode, but you can change it back to "Regular", using this dropdown. affects the data collected as the control solution was left to sit when other dilutions were being A reaction is in a state of, dynamic equilibrium once the rate of the products formed from reactant is equal to the rate of the, products being consumed to form reactants. The Students who do not complete the WebAssign prelab are required to bring and hand in the prelab worksheet. Using the Spec 20 UV-visible spectrometer, we will be studying this equilibrium. E6S2)212 "l+&Y4P%\%g|eTI (L 0_&l2E 9r9h xgIbifSb1+MxL0oE%YmhYh~S=zU&AYl/ $ZU m@O l^'lsk.+7o9V;?#I3eEKDd9i,UQ h6'~khu_ }9PIo= C#$n?z}[1 r;Jli# v#[^alqE|x{/qA:\%{#7eiNUJoJcP6}%M02-/9Q5N"1 >> Rinse and dry all your glassware with water and return it to the set-up area where you found it. To determine the equilibrium constant for the reaction: To gain more practice using a pipet properly. Concentration of [FeSCN]2+(M) The equation M1V1=M2V2 was used to calculate the initial values of [SCN-]I and the dilution factor (V2/V1) was also taken into account. << /Length 5 0 R /Filter /FlateDecode >> 2z&_=C,q UNe,yG ?'|yL"oDW#4!3"#aY:G5 x6_,Qo%d concentration (M) and its absorbance are directly proportional. 23/09/, INTRODUCTION Accessibility StatementFor more information contact us atinfo@libretexts.orgor check out our status page at https://status.libretexts.org. Please print the worksheet for this lab. In this method, the path length, \(l\), is the same for all measurements. Ultimately, the specific wavelength is determined by determining the maximum that the experiment was done in an open system where we used beakers and cuvettes. The equilibrium constant for equation 4 can be expressed using the concentrations of the three components: ( 5 ) K =. To gain practice plotting a calibration curve and use it to determine the concentration of an unknown solution. Lab 3B: Spectrophotometric Determination of Equilibrium Constant. (M) and its absorbance are directly proportional. 1 3217. As such, the absorbance is directly related to the concentration of \(\ce{FeSCN^{2+}}\). for each of the six Avoid contact with skin and eyes. endobj 3 Therefore, the objective of this lab was to calculate the Keq, through the experimental determination of [FeSCN]2+ when in equilibrium with [Fe3+] and, The data collected from this experiment demonstrate that the average Kc value for the, formation of FeSCN2+ was determined to be 1563 with a percent error of 84%. 1 252. STD 1454. an Equilibrium Constant. procedure of this lab might have been done with low precision. When iron (III) nitrate is added to water, the Fe3+ ions are hydrated, producing hexaaquairon (III) ions which form a yellow color. j): Nitric acid is listed as a corrosive. Overall, the Keq values of all six samples, centred around the mean Keq value of 249.036, with no outliers present in the data. In order to, determine the equilibrium concentrations of both reactants and products, an ICE table was. The equilibrium expression for the reaction in Equation 1 is given as: K eq = [C] c [D]d (Eqn. The absorbance, \(A\), is directly proportional to two parameters: \(c\) (the compound's molar concentration) and path length, \(l\) (the length of the sample through which the light travels). K Background In the study of chemical reactions . An Equilibrium Consta nt. Sample. Values below 0, or above 0 will result in a loss of %PDF-1.3 For the future, to minimize the percent error in You will use a standard This experiment determines Kc for an equilibrium system in which all species are ionic and soluble. spectrophotometry can be used to determine the concentrations of the varying solutions. stream Table 2: Concentrations (M) of SCN- and Fe3+ calculated using the equation M 1 V 1 =M 2 V 2 for 2 0 obj affect our lab results, as they are not ideal values. Fe3+ (aq) + SCN- (aq) FeSCN2+ (aq) The equilibrium constant, Keq, is defined by the equation shown below. There are not many potential sources of error in this experiment, as it was done through a simulation, which drastically decreases the chances of systematic (inaccurately calibrated instrument) and random errors (human perception error) which may have occurred during an in-person experiment. Sample Number Absorbance 0000085690 00000 n
thiocyanate ions, SCN-. 2 .300 No, a maximum absorbance value of 2.0000 should not be used as it varies drastically from the ideal values between the ranges of 0.2 and 0.5 for Beers Law to take effect. 2003-2023 Chegg Inc. All rights reserved. These are prepared by mixing a small amount of dilute \(\ce{KSCN}\) solution with a more concentrated solution of \(\ce{Fe(NO_{3})_{3}}\). 2 291. Chem 122L: Principles of Chemistry II Laboratory, { "01:_Laboratory_Equipment" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.
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