Procedure When obtaining solutions in this experiment, be very careful to obtain solutions with the correct concentration. 442 M), the reaction will shift so that a new equilibrium is reached. Remember to calibrate the instrument. Compare your value to this litera. Because H 2 O is the only non-condensed phase present, the equilibrium constant is P(H 2 O) 3 = (. Agreement is quite good with the data of Burrows et al. Furthermore, the equilibrium constant for this reaction, which de-pends on the second ionization constant of H 2 S, is poorly known. equilibrium constant, the activity coefficient and the Davies parameters are all temperature-dependent, thermal regulation at 25°C is necessary. 20 n D = 22 D + (22 -20)*0. Reactions always reach equilibrium. Standard Electrode Potentials at 25 â C Reduction Half-Re. The Effect of Temperature on the Position of the Equilibrium and the K eq. If you're behind a web filter, please make sure that the domains *. 10 points if you do. joshua farley chem 1252l 3/18/2015 le châtlier’s principle introduction le châtlier’s principle relates the equilibrium position of reaction to external. In Part A of this experiment, you will prepare FeSCN2+ solutions of known concentrations, mea-. These are the varying amounts of Fe(NO3)3, KSCN, and H2O. a dynamic condition where two opposite changes occur at equal rates Chemical reactions: the forward rate of reaction = the reverse rate of rxn. 105] The relationship between the temperature of a reaction, its standard enthalpy change, and the equilibrium constant at that temperature can be expressed as the following linear equation: (a) Explain how this equation can be used to determine Δ H ° experimentally from the equilibrium constants at several different temperatures. Example: Estimate the solubility of Ag 2 CrO 4 in pure water if the solubility product constant for silver chromate is 1. If you're behind a web filter, please make sure that the domains *. and im sure u know that in this case. ex: equilibrium expression and numerical value Keq is equilibrium constant. Michael Evans — Georgia Institute of Technology. Apart from the reactions tabulated in Table S1 in the SI, the. It is equal to the product of the concentration of ions in solution. As cold (or hot) air leaks into the house, the FeSCN2+) 3. The numeric values for this example have been determined experimentally. 2 × 10 -4 M 0. The equilibrium reaction has a very high Kc. If you could find the value and cite the source, it would be greatly appreciated. Procedure When obtaining solutions in this experiment, be very careful to obtain solutions with the correct concentration. 63 mV K-1 a reaction entropy S = - 121 J·K-1·mol-1 can be calculated. While the reaction reached equilibrium, the absorbance measured at 447 nm was equal to 0. This experiment will probe the equilibrium of Fe(III) ions reacting with the thiocyanate ion, SCN. Page I-4 / Determination of an Equilibrium Constant Lab FeSCN2+ using Le Chatelier's Principle. Investigating Iron Thiocyanate Revised: 4/28/15 3 [SCN-]eq = [SCN-]i - [FeNCS2+]eq (4) Knowing the values of [Fe3+]eq, [SCN-]eq, and [FeNCS2+]eq, the value of Kc, the equilibrium constant, can be calculated. Aubrey High School PreAP -Chemistry Name _____ Period ___ Date ___/___/___ 9 Equilibrium 9. 5 Calculate K. temperature, agitation speed, activation time and decrease in initial dye concentration. 50 mL increments of 0. The first run should be done with the lowest Fe. Mérienne et al. Chemical Equilibrium. If you're seeing this message, it means we're having trouble loading external resources on our website. 10 mL increments of 0. Over moderate temperature ranges a plot of ln K p as a function of (1/T) gives a straight line with slope -∆H/R. Preppqare 5 solutions + 1 blank and allow equilibrium to establish from 5 different starting points. The effects obtained with 5% dioxane (0. 8 9 LEARNING GOAL Write equilibrium-constant expressions and use these expressions to calculate equilibrium constants. The temperature of 25oC (298. Ksp solubility product constants of many popular salts at SolubilityOFthings If there are any other salts for which you know the value of the constant, please let us know and we will update the table. We’ve been featured in The New York Times, NBC News, Univision, and more. Over moderate temperature ranges a plot of ln K p as a function of (1/T) gives a straight line with slope –∆H/R. Since the cuvet is so far from room temperature, the absorbance will not totally stabilize. thiocyanate, FeSCN 2+, will be studied and its equilibrium constant determined using a Vernier Spectrometer. This initial volume (flask + syringe) and the room temperature should be recorded in the table below as your first data point. The best-fit value for the molal equilibrium constant at 25C is 69810 and the corresponding partial molal enthalphy, entropy, and heat capacity of formation are: Ho=–17. Gently tap the syringe to allow the plunger to reach an equilibrium position. 0007925 M, SCN= 0. Write the equation and the equilibrium. Room temperature and humidity are the factors. At equilibrium, (FeSCN2+ = 1. calculate the value of the equilibrium constant (Kc). Also shown in this table are solubility products or SSP, which is the equilibrium constant for a solid dissolving in water. How constant were your K c values at room temperature? Explain any variation. Equilibrium Constant For Fescn2+ At Room Temperature Literature Value. 3 at this temperature. Use the equilibrium concentrations of the reactants and product to calculate equilibrium constants for each of the six trials. CHEM113L General Chemistry II Lab Rose-Hulman Institute of Technology Prof. I tried the CRC handbook and had trouble. Add 5 mL of distilled water to the test tube after you record the temperature. 70 x 10-5 mol HSCN. Chemical Equilibrium ⇌. By varying the amounts of reactants used and observing the amount of product generated, it will be determined whether the reaction goes to completion or reaches equilibrium. Find K c for Fe. By comparison with the literature, the purity of the sample can be evaluated. 00 x 10 −4 M x ⎯⎯⎯⎯ = 1. First, the observed refractive index has to be corrected to the temperature of the literature. 53 mol of SO2(g) in order to form 1. - A different equilibrium position will be achieved but the value of Kc will be unchanged, as long as the temperature remains the same. asked by Chemistry on October 2, 2013; chemistry. Fe3+ + SCN FeSCN2+ Rxn 1 Fe3+ + 2SCN Fe(SCN) 2 + Rxn 2. Find the value of the equilibrium constant for formation of \(\ce{FeSCN^{2+}}\) by using the visible light absorption of the complex ion. Example #1: H 2 (g) resulting in a larger value for the K eq after the position of the equilibrium has shifted. 442 M), the reaction will shift so that a new equilibrium is reached. which can contribute uncertainty to the measurement. 2, are much smaller than the value at 25 °C. Finally to analyze our experimental data graphical method is used and a graph is. The main objective of the study was to determine the influence of extractives on the equilibrium moisture content and dimensional stability. 0C using emf measurements in low ionic strength media. 2 The forward and reverse processes will proceed until there is no net change in the amount. The equilibrium constant is K = 49. (iii) State and explain the effect of increasing temperature on the equilibrium constant above given that the dissociation of water is an endothermic process. Reactions always reach equilibrium. below this temperature the reaction is spontaneous. Subtract 32 Fahrenheit degrees from 70 Fahrenheit degrees to get the number of Fahrenheit degrees above freezing. 57 M) are similar to that with 2 M ethylene glycol. The temperature dependence of the CSA formation constants can be translated into an altitude dependence, given a typical atmospheric temperature profile and the results for benzoic sulfuric anhydride are shown in Figure 3. 15 g of NH3 at some temperature. 00-L flask contains 0. 0 L flask and allowed to react at constant temperature. As a matter of fact equation (6) follows at sight by applying the mass action law to the very evident equation: H+ + CaCO, (solid) $ Ca++ + HCO; The lengthy development, however, has been presented so that the equilibrium constants could be calculated from others that are defined in the literature. This experiment will probe the equilibrium of Fe(III) ions reacting with the thiocyanate ion, SCN. Compare your value to this litera. Solubility products do change with temperature, so it is important to always note the temperature at which the solubility is measured because more of the borax solid is dissolving. Put the Erlenmeyer flask on the magnetic stirrer at room temperature. Clearly, a low-temperature equilibrium favors the production of ammonia more than a hightemperature one. Theory: Colorimetric methods of analysis are usually applied to the determination of small concentrations of either inorganic or organic materials in a solution. Equilibrium constants are dimensionless. 105] The relationship between the temperature of a reaction, its standard enthalpy change, and the equilibrium constant at that temperature can be expressed as the following linear equation: (a) Explain how this equation can be used to determine Δ H ° experimentally from the equilibrium constants at several different temperatures. 15 K) is often chosen for this reporting temperature. 1 BUILDING THE THERMODYNAMIC DATABASE. The equilibrium constants at some temperature are given for the following reactions:2 NO(g) N2(g) + O2(g) Kc = 2. 50 mL increments of 0. What is the equilibrium constant value, k for the formation of FeSCN. products is expressed by the equilibrium constant, K. 442 M), the reaction will shift so that a new equilibrium is reached. For example, the gas in a cylinder with a movable piston will be at equilibrium if the temperature and pressure inside are uniform and if the restraining force on the piston is just sufficient to keep it from moving. The reaction has two possible products given below, in lab this week you will determine which of these two reactions actually occurs. 2NO2(g) [pic] N2O4(g) Kc = 0. Chemistry 12 Santa Monica College Determination of Kc for a Complex Ion Formation Objectives • • Find the value of the equilibrium constant for formation of FeSCN2+ by using the visible light absorption of the complex ion. 2 for determining binding constants – at room temperature. At a particular temperature the equilibrium constant for the reaction: H2(g) + F2(g) ? 2HF(g) is K = 36. If enough of a monoprotic acid is dissolved in water to produce a 0. 563 M is at equilibrium; for this mixture, Q c = K c = 50. 4 kcal / mol DG = B Shifting the equilibrium ratio…. 500 mol iodine (I 2) are placed in a 1. 105] The relationship between the temperature of a reaction, its standard enthalpy change, and the equilibrium constant at that temperature can be expressed as the following linear equation: (a) Explain how this equation can be used to determine Δ H ° experimentally from the equilibrium constants at several different temperatures. The equilibrium constant for a reaction at room temperature is K 1 and that at 700 K is K 2. An effective temperature for the reaction equilibrium constants at non-zero electric field was empirically obtained using a parameter describing the electric field dependence of the reaction equilibrium constants. 12M, [H 2] = 1. No temperature is specified. Measure the absorbance of the 5 equilibrium solutions at wavelength, = 447 nm Determine the equilibrium [FeSCN 2+] from the calibration curve from Part A. 0150 M solution with a pH of 6. 7 Discuss the implications of your observations, basing your discussion on your knowledge of Le value of the extinction coe cient for FeSCN2+ at its. products is expressed by the equilibrium constant, K. The apparent acid dissociation constant (Kc) of benzoic acid in water has been determined titri-metrically under ionic strength values between 0. rate constant for the reaction Fe3+ + SCN– → FeSCN2+. The concepts of equilibrium and thermodynamics are among the most important topics covered in a general chemistry course. 2, are much smaller than the value at 25 °C. 0020 M KSCN to a 100 mL beaker. Disruption of equilibrium: Changes in temperature - that Kc is temperature dependent, so changing the temperature will change Kc. There are two different thiocyanate solutions, and two different iron. Fe 3+ + SCN-⇋ [FeSCN] 2- Reaction 1". Calculate the equilibrium concentrations of the water, ethyl ethanoate, ethanoic acid and ethanol in the mixture and hence the equilibrium constant. 170 Reference Solution #2 6. 42 moles each of hydrogen and fluorine gases plus 0. , the ester will react with water to form a carboxylic acid and an alcohol). k on and k off were determined from this figure, and the K d were then calculated as the k off /k on ratio. 50 mL increments of 0. Apart from the reactions tabulated in Table S1 in the SI, the. products is expressed by the equilibrium constant, K. 2NO2(g) [pic] N2O4(g) Kc = 0. Source: Laboratory of Dr. Rate constants for chemical reactions in high-temperature nonequilibrium air. Write the equilibrium constant expression for the formation of FeNCS 2+ ion, based on the stoichiometric relationship in Equation 5. Calculate the average K c for the six trials. 24, K sp = [Ni 2+][L −] 2 = 10 −23. She finds that in the equilibrium mixture, the concentration of FeSCN2+ is 1. (iii) State and explain the effect of increasing temperature on the equilibrium constant above given that the dissociation of water is an endothermic process. The equilibrium constant expression for this process would be. Equilibrium is shifted to the N 2 O 4 side upon a decrease in temperature. It also noteworthy, that, just like any equilibrium expression, each. 50 g) under a constant agitation speed of 170 rpm at room temperature for constant exposure time (60 min). The reaction is represented by the following equation: Fe 3+ + SCN - <—-> FeSCN 2+. When the test tube is placed in an ice bath, the low temperature causes the equilibrium constant of the solution decreases and hence the formation of solid copper(II) nitrate is increases. Explain why there may be an infinite number of values for the reaction quotient of a reaction at a given temperature but there can be only one value for the equilibrium constant at that temperature. The equilibrium for the reaction to be studied is actually a solubility product constant, K. After equilibrium is reached, 0. K = C % D ' A) B + All closed chemical reactions eventually reach their equilibrium state, where the speeds of the forward and reverse reactions are equal. xls) calculates the Henry's law constant for the respective minimum and maximum temperatures denoted by T min and T max. Equilibrium constants for the reaction of aryl thiol anions with hydroxyethyl disulfide have been measured which, along with literature data, demonstrate a slope of 1. 600M Calculate the value of the equilibrium constant. Immerse the flask in the lowest temperature water bath and allow the plunger to come to equilibrium. Comparison of Literature values. Michael Evans — Georgia Institute of Technology. O estudo do espectro solar ficava facilitado durante os eclipses, quando se podia observar apenas a borda do disco solar, sem os problemas normais de ofuscamento. [64] Perner et al. The calorimeter should not be disturbed for at least 2 min to allow the water to reach thermal equilibrium (constant temperature reading. 15 moles of HF. The equilibrium constant for this reaction changes with temperature, as shown in the table below. Time-resolved fluorescence spectroscopy and global analysis of fluorescence decay times were applied to determine stoichiometry and equilibrium constants of complexes of tyrosine with α-, β- and γ-cyclodextrins (CDs). In this two-part lab, students will determine the equilibrium constant for the reaction of iron (III) ions with thiocyanate ions (SCN-). Equilibrium parameter RL value was calculated as 0. For your first trial, after preparing the sample as described in the lab manual, the absorbance of tube #1 is 0. An evaluation by. For the ice/cold water solutions, you should record the maximum value of the. 12M, [H 2] = 1. The value of Kc for the reaction PCl5 (g) ⇋ PCl3 (g) + Cl2 (g) will be NEXT When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place and the reaction. 10 mL increments of 0. Data Tables Data Table 1 — Reference Solutions Temperature Sample [FeSCN 2+] eq * Absorbance Reference Solution #1 4. It depends on the ionic strength and temperature and is independent of the concentrations of reactants and products in a solution. The concentration of FeSCN 2+ will be measured and the concentrations of Fe 3+ and SCN - will be calculated. When a system is at equilibrium, the rate at which products form from reactants is the same as the rate at which products are decomposing to produce reactants. 362 Reference Solution #4 1. [53] to obtain the equilibrium constant. 3M Notice the 3 sd’s in all your data. So, there is no net change in concentrations at equilibrium. In the nonequilibrium atmospheric chemistry regime that will be encountered by the proposed Aeroassisted Orbital Transfer Vehicle in the upper atmosphere, where air density is too low for thermal and chemical equilibrium to be maintained, the detailed high. The equilibrium position shifts to the left at the condition of 0. 42 moles each of hydrogen and fluorine gases plus 0. Kc = (b) The table below shows the value of the equilibrium constant, Kc at two different temperatures. Later, you will prepare an equilibrium solution at a temperature near 100 °C and measure the new value of the equilibrium constant. When the cuvet in the ice water bath has equilibrated, measure its temperature and absorbance as described in step 13. 00100 M KSCN are added to 4. Given the equilibrium: 2A + B A 2B Keq = 2. 15 K in this work is K = = = 12. What is the literature value equilibrium constant (Keq) for FeSCN2+? I found reports varying from 138-890. equilibrium represents a balance between forward and reverse reactions to give a fixed value for the equilibrium constant (K) at a fixed temperature. ); If one reactant is added in extreme excess, the reaction will approach. For the dissociation of an insoluble salt the equilibrium constant is the solubility product, K. 24, K sp = [Ni 2+][L −] 2 = 10 −23. No temperature is specified. For the reaction at equilibrium: 3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g), removing some of the product, Fe3O4(s), would: Answer A. (1) Calibrate the colorimeter. Question What is the value of the equilibrium constant at room temperature for the following reaction? Fe3+(aq) + SCN-(aq) Fe(SCN)2+(aq) Prediction Write the equilibrium expression for this reaction. The use of an absorption path length of 61m allowed them to work at very low pressure (<0. The actual concentration of the FeSCN 2+ complex present at equilibrium in a solution may be obtained by comparing its color with standard solution, in which the concentration of FeSCN 2+ is known. 1, the percent difference is 1. Equilibrium constants are dependent upon the temperature of the system. 442 M), the reaction will shift so that a new equilibrium is reached. Always label all glassware before adding solutions. This thesis is concerned with the design, development and implementation of Microcomputer-Based Laboratory experiments appropriate for Chemistry 11 and 12 in British Columbia. In order to assess the purity of the compound, the observed refractive index has to be corrected towards the literature conditions (temperature here), not vice versa. Qc, for a reaction has a value of 75 while the equilibrium constant, Kc, has a value of 195. The equilibrium concentration of FeSCN2+ ([FeSCN2+]std) for this standard solution is assumed to be_____M? What permits this assumption? A. product are related by the equilibrium constant of the reaction; in this case, the formation constant K f: Kf = [FeNCS 2+]eq [Fe 3+]eq [NCS –]eq 2 Kf can be calculated through an experimental determination of the equilibrium concentration of the complex, [FeNCS 2+]eq, in equilibrium with [Fe 3+]eq and [NCS –]eq. 3-5 the thermodynamics of a chemical reaction are completely characterized by measuring the equilibrium constant as a function of temperature; the reaction ∆G, ∆H, and ∆S are all determined. However, this reaction proceeds slowly at room temperature so lowering temperature to shift equilibrium was not a good option. Repeat step 4, 5 and 6 to mark the solution level as 2 and record the equilibrium temperature. At equilibrium the concentration of each substance remains constant. The object of this experiment is to determine the value for the equilibrium constant for reaction (1). 00 x 10-6 mol = 1. The equilibrium constant ure will increase the value of K‡ since this is an endothermic reaction. Therefore, the value of K c in this expression also remains constant: [FeSCN+2] K c = (eq. [Sub] were fitted by eq. 04 Torr) and to minimize the influence of. [11] and the room temperature data of Tuazon et al. No temperature is specified. In this experiment, you will determine the value of K eq for the reaction between iron (III) ions and thiocyanate ions, SCN-. An equilibrium constant can then be determined for each mixture; the average should be the equilibrium constant value for the formation of the FeSCN2+ ion. ) Record the temperature to the nearest 0. 0L flask contains: 0. adsorbents (0. 15 moles of HF. See if you can find literature and/or i nternet references for the equilibrium constant for this equilibrium. Confirm the stoichiometry of the reaction. A carboxylic acid will react with an alcohol to form an ester and water in a reversible reaction (i. However, this reaction proceeds slowly at room temperature so lowering temperature to shift equilibrium was not a good option. 00 x 10-3 M Fe(NO 3) 3 with 5. 0020 M KSCN. 4 at 410 nm. Explain why an equilibrium between Br 2 ( l ) and Br 2 ( g ) would not be established if the container were not a closed vessel shown in Figure 4. These variables include the ones discussed in class such as pressure and temperature. It is really important to write down the equilibrium reaction whenever you talk about an equilibrium constant. The effect of temperature on the solubility product constant, Ksp, of potassium hydrogen tartrate in water was investigated in the temperature range of 285K to 318K at normal atmospheric pressure. The value of ∆H is often negative. 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. Room temperature and humidity are the factors. occurred; for every mole of FeSCN 2+ that is formed, one mole of Fe 3+ and one mole of SCN-will react. 200 M Fe(NO3)3, and for the equilibrium solutions, 0. It also noteworthy, that, just like any equilibrium expression, each. the equilibrium by distillation, which increases the yield. The effect of a change in volume on gaseous equilibria is described in Chemistry 2, Chapter 9. Thus, a measured value of 75. Based on the results, predict and explain the magnitude of the equilibrium constant at room temperature. Chemical Equilibrium ⇌. The purpose of this lab is to experimentally determine the equilibrium constant, K c, for the following chemical reaction:. adsorbents (0. 0000005 M, FeSCN 2+ = 0. We have to ensure that only valid information is provided by our website. The first run should be done with the lowest Fe. 10 mL increments of 0. The following information should allow you to develop a research plan for evaluating the equilibrium constant of the iron (II) thiocyanate ion in aqueous solution. 00 mol Cl2 is placed in a 1. (1) Using pressure as our variable and treating the species as ideal gases, we can write the equilibrium constant as K(T) = P P NO 2 N O 2 2 4. C12-4-02 Write equilibrium law expressions from balanced chemical equations for heterogeneous and homogeneous systems. Therefore, cooling the reaction mixture favors the formation of even more ammonia. A K number ~ 1000 or more is very large and it means there are. Explanation (including important chemical equations): 2 NO 2 (g) => N 2 O 4 (g). In the study of chemical reactions, chemistry students first study reactions that go to completion. At a certain temperature, the equilibrium constant for the following chemical equation is 2. Aubrey High School PreAP -Chemistry Name _____ Period ___ Date ___/___/___ 9 Equilibrium 9. Consider calcium sulfate, which is moderately insoluble. 20 * 10-4 M in this example. (DO NOT forget to measure the room temperature) 4. k A slope as defined by equation (3. ex: equilibrium expression and numerical value Keq is equilibrium constant. The adsorption data was follow. Once this is. Introduction. She finds that in the equilibrium mixture, the concentration of FeSCN2+ is 1. The best-fit value for the molal equilibrium constant at 25C is 69810 and the corresponding partial molal enthalphy, entropy, and heat capacity of formation are: Ho=–17. If Keq is a small number (<1) then the chemical equilibrium favors the formation of reactants (large denominator). (DO NOT forget to measure the room temperature) 4. 30 M: reaction at that temperature. The equilibrium between nitrogen dioxide, NO2, and dinitrogen tetroxide, N2O4, is shown below. 170 Reference Solution #2 6. These theoretical values of temperature are shown in the final column of Table A-1. Temperature: constant. In the nonequilibrium atmospheric chemistry regime that will be encountered by the proposed Aeroassisted Orbital Transfer Vehicle in the upper atmosphere, where air density is too low for thermal and chemical equilibrium to be maintained, the detailed high. 0000005 M, FeSCN 2+ = 0. of the products and reactants at equilibrium. 15 K) is often chosen for this reporting temperature. The equilibrium constant for this equilibrium is. These are the varying amounts of Fe(NO3)3, KSCN, and H2O. The equilibrium concentration of FeSCN2+ ([FeSCN2+]std) for this standard solution is assumed to be_____M? What permits this assumption? A. Hence, knowing [FeSCN 2+ (aq)],[ Fe 3+ (aq)] and [SCN-(aq)] at equilibrium allows you to determine the value of Q (K) for each reaction mixture. Determination of an Equilibrium Constant Abstract: In this experiment, two reactions were run to determine the molar absorptivity and the equilibrium constant of FeSCN2+. The values for equilibrium constants that you find in reference books are usually measured at 25 °C, roughly room temperature. The well-known colorimetric determination of the equilibrium constant of the iron(III)−thiocyanate complex is simplified by preparing solutions in a cuvette. The equilibrium constant for the equilibrium CO(g) + H2O(g) ⇌CO2(g) + H2(g) is 302 at 600K. All that is needed is the value of the equilibrium constant K at 298. Solubility is defined as the upper limit of solute that can be dissolved in a given amount of solvent at equilibrium. If Keq is a small number (<1) then the chemical equilibrium favors the formation of reactants (large denominator). Ksp =[A2+]3[B3-]2. Determination Of Keq For Fescn2 Lab Answers. Chemical equilibrium. 0020 M KSCN to a 100 mL beaker. Using these values, determine the degree of dissociation and the equilibrium constant, K p, ΔGo and ΔSo for the dissociation at each temperature. Equilibrium Constant and Temperature: How Does a Change in Temperature Affect the Value of the Equilibrium Constant for an Exothermic Reaction? Introduction. (room temp) water in the calorimeter which is equilibrium constant of FeSCN2+ 3) initial - equilibrium FeSCN to find equilibrium concentrations of Fe3+ and SCN-. 00200 M Fe. The effect of a change in volume on gaseous equilibria is described in Chemistry 2, Chapter 9. The guideposts are not very detailed - and yet this series of calculations requires several steps that are linked together to come up with a final. 400M [H 2 O] = 0. Fe^3+(aq) + B(s) + 6H_2O(l) rightarrow Fe(s) + H_3BO_3(s) +. [hint: Beer's Law says that absorbance is directly proportional to concentration] Absorbances are as follows: a) 2. 362 Reference Solution #4 1. Question: How do we measure the equilibrium constant for a reaction? Pre-lab Objective: In this experiment, you will determine the equilibrium constant, Kc, In all the solutions used in the experiment, [H+] will be maintained at a value of. 10 mL increments of 0. The equilibrium constant, Ksp, was calculated at each temperature from the molarity, and ∆G was determined from Ksp. A saturated solution of calcium hydroxide has the solid in equilibrium with its ions as shown below: Ca(OH)2(s) ↔ Ca2+(aq) + 2OH-(aq) Recall that a saturated solution is a solution that contains the maximum amount of dissolved solute possible at a given temperature. Its value at room temperature will be approximately 1/4 (0. 10Œ3 M) and air (ca. Answer _____ 5. The acid dissociation constant is the equilibrium constant of the dissociation reaction of an acid and is denoted by K a. The initial amounts of Fe3+ and SCN-can be calculated. The endothermic reaction is favoured. Because the quotient is a constant, the so-called equilibrium constant Kc, the numerator also has to decrease: The equilibrium is displaced towards the reactant side, i. Get Your Custom Essay on Solution Calorimetry: Thermodynamics of Potassium Nitrate Just from $13,9/Page. The equilibrium constant decreases from 9 × 10 5 M ‐1 in aqueous phosphate buffer to 5. ); If one reactant is added in extreme excess, the reaction will approach. The Organic Chemistry Tutor 1,424,154 views. occurred; for every mole of FeSCN 2+ that is formed, one mole of Fe 3+ and one mole of SCN-will react. permitted a different approach to equilibrium. 90 x 10-4, would the mixture yield more products, more reactants or is it. In this example, ε = 3625 M-1cm-1 Part B: The Equilibrium Constant In the second series of reactions, neither Fe3+ (aq) nor SCN − (aq) will be present in vast excess. The reaction has two possible products given below, in lab this week you will determine which of these two reactions actually occurs. termine the value of the room temperature equilibrium constant (K c) for the formation of the Fe(SCN)2+ ion. Chapter 13. Predict the effect of temperature on the Equilibrium constant of the above reaction. 50 mL increments of 0. 20 M, [FeSCN2+] = 0. 00200 M KSCN are added to 4. The Excel spreadsheet program from the companion website (Henry's-law-constant. The concentration of FeSCN 2+ will be measured and the concentrations of Fe 3+ and SCN - will be calculated. 12M, [H 2] = 1. Given the equilibrium: 2 NO 2(g) N 2O 4(g) Keq = 2. Haber Process: N 2( g ) + 3H 2( g ) ⇌ 2NH 3( g ). 35 g of H2, and 2. Changing the temperature of a system at equilibrium has a different effect: A change in temperature actually changes the value of the equilibrium constant. The initial amounts of Fe3+ and SCN-can be calculated. Return to Equilibrium menu. As cold (or hot) air leaks into the house, the FeSCN2+) 3. Describe the effect of changing the temperature, pressure , volume, concentration or adding a catalyst on the value of the equilibrium constant. In this experiment, you will determine the value of K eq for the reaction between iron (III) ions and thiocyanate ions, SCN-. If the temperature of a reaction mixture is changed, the equilibrium will shift to minimise that change. Its value at room temperature will be approximately 1/4 (0. It is really important to write down the equilibrium reaction whenever you talk about an equilibrium constant. It states that: At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. The subscript eq on the equilibrium contant means that it is defined in terms. The first reaction was run to completion using LeChatier's Principle and the second reaction was run to equilibrium. The following information should allow you to develop a research plan for evaluating the equilibrium constant of the iron (II) thiocyanate ion in aqueous solution. To prepare the standard solution, the complex is formed from Fe 3+ and SCN- ions, using a very high concentration of Fe 3+ ions. of the products and reactants at equilibrium. Equilibrium Moisture Content is the moisture content that wood will eventually reach given exposure to the same conditions around the wood. Fe3+(aq) + SCN¯ (aq) FeSCN2+ (aq) (1) Associated with this reaction is an equilibrium constant K, which varies with temperature depending on the exo- or endo-thermicity of the reaction. 70 x 10-5 mol HSCN. one FeSCN+2, another FeSCN+2 dissociates to become Fe+3 and SCN-. 23 − 138 138 = 181 error. When compared to the literature pK c value of 7. 00200 M KSCN are added to 4. The equilibrium reaction has a very high Kc. Knowing the values of [Fe3+]eq, [SCN–]eq, and [FeNCS2+]eq, the value of Kc, the equilibrium constant, can be calculated. The acid dissociation constant is the equilibrium constant of the dissociation reaction of an acid and is denoted by K a. (DO NOT forget to measure the room temperature) 4. In this experiment you will use this method to find the equilibrium constant for the reaction between carbon monoxide, carbon dioxide and carbon as a function of temperature. Learn vocabulary, terms, and more with flashcards, games, and other study tools. products is expressed by the equilibrium constant, K. 10 mL increments of 0. Record this temperature. One point is earned for the correct justification. What is the accepted value of. We will do this first in a solution at room temperature. Kc = (b) The table below shows the value of the equilibrium constant, Kc at two different temperatures. Write the equilibrium constant expression for the formation of FeNCS 2+ ion, based on the stoichiometric relationship in Equation 5. From fitted Raman spectra, equilibrium constants Kn+1 (UO2Cln2-n ((aq)) + Cl-(aq)(-) = UO2Cln+11-n ((aq))) have been calculated as a function of temperature and chlorinity. The equilibrium data was better fitted by Langmuir isotherm model than other isotherm models. some iron thiocyanate complex has to decompose again into iron hexaquo complex cations and thiocyanate anions. Using eqs 1 and 2 above, students derive an expression for the equilibrium concentration of iron(III) thiocyanate using K o b s: [FeSCN 2. Solubility Product Constant of Silver Acetate Titrate to determine the concentration of Ag + in the saturated solution and calculate the concentration of OAc - to determine K sp Investigate the effects of temperature on K sp Fe3+(aq) + SCN-(aq) FeSCN2+(aq ) red complex Equivalence point, precipitate titration End point, complex formation. our example were obtained at a different temperature and thus relate to a different value of Kc. of the products and reactants at equilibrium. (This wavelength is referred to as the λ max. From fitted Raman spectra, equilibrium constants Kn+1 (UO2Cln2-n ((aq)) + Cl-(aq)(-) = UO2Cln+11-n ((aq))) have been calculated as a function of temperature and chlorinity. Compare your value to this litera. If you could find the value and cite the source, it would be greatly appreciated. The expression for the equilibrium constant for this reaction is: Kc = [A2+]3[B3-]2 [A3B2] Since A3B2 is a solid, its concentration is always the same. While individual ions continue to change in this way, there is no net change in the amount of any reactant or product. 5 at 357 °C to 50. RT is a measure of 'thermal energy'. Time-resolved fluorescence spectroscopy and global analysis of fluorescence decay times were applied to determine stoichiometry and equilibrium constants of complexes of tyrosine with α-, β- and γ-cyclodextrins (CDs). k2 A rate constant (Appendix C. 850 mol each of N 2 and O 2 are introduced into a 15. Fourth, substitute the equilibrium concentrations into the equilibrium expression and solve for K sp. The purpose of this lab is to experimentally determine the equilibrium constant, K c, for the following chemical reaction: When Fe 3+ and SCN-are combined, equilibrium is established between these two ions and the FeSCN 2+ ion. How constant were your K c values at room temperature? Explain any variation. Addition of small amounts of ice or warm water to the water jacket will maintain this temperature, as the reaction is only slightly exothermic. ex: equilibrium expression and numerical value Keq is equilibrium constant. A reaction mixture in a 10. The method of determining the equilibrium constant in this experiment is worth discussing. The equilibrium data was better fitted by Langmuir isotherm model than other isotherm models. Stephany Matos Chem Lab: Chemical Equilibrium Lab 52 Synopsis Iron (III) ions react with thiocyanate ions (SCN-) to form iron (III) thiocyanate, FeSCN2+. thiocyanate, FeSCN 2+, will be studied and its equilibrium constant determined using a Vernier Spectrometer. So, there is no net change in concentrations at equilibrium. O 2 (aq) O 2 (g). However, this reaction proceeds slowly at room temperature so lowering temperature to shift equilibrium was not a good option. Pour, under constant stirring, 50 mL of distilled water, 40 mL acetone, 0. The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency towards further change. 20 Electrochemistry in Equilibrium To be published as: Experimental Electrochemistry at WILEY-VCH Fig. 442 M), the reaction will shift so that a new equilibrium is reached. 16 times the triple point temperature. until virtually all the SCN– is converted to FeSCN2+. Using the absorbance values obtained by the class for each of the known concentrations,. 5), or the Boltzmann constant (Appendix C. Then, I would move to the K eq expression to discuss the effect on the constant of increasing and decreasing the amounts of. our example were obtained at a different temperature and thus relate to a different value of Kc. 10 mL increments of 0. 850 mol each of N 2 and O 2 are introduced into a 15. 00 x 10-3 M Fe(NO 3) 3 with 5. Therefore, the assumption that the value of Ksp is dependent only on temperature at which the dissolution occurs can be established. According to the data, the calculated equilibrium constant of the bromothymol blue indicator was (1. 2 * 104 at room temperature. The literature value will be used as a comparison for the calculated equilibrium constant. The values are usually given in the form of an equilibrium constant, K, which takes the form: K c = [C]⋅[D] [A]⋅[B] The c on K c refers to the concentrations of the species in the reaction. When the cuvet in the ice water bath has equilibrated, measure its temperature and absorbance as described in step 13. However, we can qualitatively predict the effect of the temperature change by treating it as a stress on the system and applying Le Châtelier’s principle. No change C. Complex ions, thiocyanatoiron(III) ions, are formed from iron(III) ions and thiocyanate ions in aqueous solution : Fe3+(aq) + SCN-(aq) <=> FeSCN2+(aq) (1) The equilibrium constant for this reaction is: Kc = [FeSCN2+(aq)] (2) [Fe3+(aq)][SCN-(aq)] The product complex ion is the only one of the three species which has an appreciable color (blood-red). 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. This equilibrium constant is a quantitative measure of the strength of an acid in a solution. ; K sp = [0. Determine the equilibrium [Fe 3+] and [SCN-] from the ICE table. One point is earned for the correct prediction. This dissolution is an equilibrium process for which an equilibrium constant can be written. some iron thiocyanate complex has to decompose again into iron hexaquo complex cations and thiocyanate anions. Equilibrium Constant Fescn | WordExplorer. THERMODYNAMIC PHASE-EQUILIBRIUM l The solubility of NH 3 in water is high at room temperature and 1atm of pressure m The solubility increases with pressure and decreases with temperature l It is possible to derive a relationship relating x to y, but we are mostly interested in cases of low values of y(use of dilute mixture of NH 3 and nitrogen). The equilibrium constant, K eq, is 54. The equilibrium constant is a thermodynamic quantity which is related to the standard Gibbs free energy change by ∆Go = -RTlnK (5) where T is the Kelvin temperature and R=8. Use your experimental value of the molar absorptivity, ε, for FeSCN2+, and the absorbance calculated for Part B, step 2, to calculate the equilibrium concentration of FeSCN2+ in the solution. Post Lab Questions: 1. 0 °C) to 10 °C above room temperature, the rate of a reaction doubles. I need the literature value for the Equilibrium Constant (Keq) of FeSCN2+, as well as the source of this value. A mixture of gases at 400 °C with [H 2] = [I 2] = 0. 4 kJ/mol: K = e +1 = 2. Standard Electrode Potentials at 25 â C Reduction Half-Re. 2 × 10 3 M −1 in 6 M ethylene glycol and to 2. Because the quotient is a constant, the so-called equilibrium constant Kc, the numerator also has to decrease: The equilibrium is displaced towards the reactant side, i. To this solution, add 25 mL of deionized water. In this experiment, you will determine the value of K eq for the reaction between iron (III) ions and thiocyanate ions, SCN-. (1) Calibrate the colorimeter. 7 x 10^-4 M. At a certain temperature, the equilibrium constant for the following chemical equation is 2. O estudo do espectro solar ficava facilitado durante os eclipses, quando se podia observar apenas a borda do disco solar, sem os problemas normais de ofuscamento. Use the slope and intercept of the Beer's Law graph to write an equation that will convert the absorbance readings into equilibrium [FeSCN2+]. The equilibrium constant is the value of the reaction quotient that is calculated from the expression for chemical equilibrium. solubility of calcium hydroxide decreases with increasing temperatures. Substituting these values into the correct expression for the equilibrium constant will give the value for Kc at the room temperature. I think that changing concentration or pressure at equilibrium is just physical pressure on system which doesn't change heat content of system so kc remain constant but temperature change at equilibrium disturb heat content of system so one species may be more favoured than other hence equilibrium constant disturb if I am wrong kindly. permitted a different approach to equilibrium. for FeSCN2+ Inquiry Guidance and AP* Chemistry Curriculum Alignment Introduction The equilibrium constant gets its name from the fact that for any reversible chemical reaction, the value of K eq is a constant at a particular temperature. 00 mol Cl2 is placed in a 1. An equilibrium constant can then be determined for each mixture; the average should be the equilibrium constant value for the formation of the FeSCN2+ ion. ; K sp = [0. For a given temperature, the numerical value of the equilibrium constant (K) for a. One point is earned for the correct justification. In this calculation, which used the ideal gas equation, the volume and mass were assumed to be constant. 15 K, which can easily be obtained from the graph and trendline discussed above. But these reactions are so slow at room temperature, that each equilibrium can be studied individually. When the cuvet in the ice water bath has equilibrated, measure its temperature and absorbance as described in step 13. Confirm the stoichiometry of the reaction. The temperature dependence of the CSA formation constants can be translated into an altitude dependence, given a typical atmospheric temperature profile and the results for benzoic sulfuric anhydride are shown in Figure 3. there has been no reaction, only A and B are present). 4 kcal / mol DG = B Shifting the equilibrium ratio…. Calculate the equilibrium concentrations of the water, ethyl ethanoate, ethanoic acid and ethanol in the mixture and hence the equilibrium constant. 15 )KK T=+ + −+ nn 0 4 (1) where the values of log K n 0 can be referred to in Table S1 in the SI. This value is t. [64] Perner et al. The equilibrium between nitrogen dioxide, NO2, and dinitrogen tetroxide, N2O4, is shown below. 62 M; [O 2] = 0. Calculate K for the reaction, shown below, at this temperature. adsorbents (0. Example: An example of calculation of the equilibrium constant is: 2SO 2 (g) + O 2 (g) ⇌ 2SO 3 (g) [SO 2] = 0. NO 2 is in the highest concentration. Calculation of Kobs Kobs will be calculated by first determining the concentrations of all species at equilibrium. The example reaction you post is a redox reaction. 36 x 10 −4 M Aref 0. The k and K values determined at various temperatures were used to. In physics, Henry's law is one of the gas laws formulated by William Henry in 1803. The thermodynamic properties ∆G°, ∆H°, and ∆S° are difficult to measure directly in a laboratory setting, but can be determined by monitoring the temperature dependence of the equilibrium constant, K. equilibrium constant). In the nonequilibrium atmospheric chemistry regime that will be encountered by the proposed Aeroassisted Orbital Transfer Vehicle in the upper atmosphere, where air density is too low for thermal and chemical equilibrium to be maintained, the detailed high. The temperature of 25oC (298. In this calculation, which used the ideal gas equation, the volume and mass were assumed to be constant. The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency towards further change. 10Œ3 M) and air (ca. These are the varying amounts of Fe(NO3)3, KSCN, and H2O. Figure 2: (a). Equilibrium constants are dimensionless. Intro to Chemistry, Basic Concepts - Periodic Table, Elements, Metric System & Unit Conversion - Duration: 3:01:41. Plot Absorbance (@ 450 nm) vs [FeSCN2+]: Graph 1: Standard Absorbance Curve for [FeSCN2+] (M) @ 450 nm Use Beer's Law: Ac= εl , εl = slope of the line, and l = 1 cm. 901 Once the equilibrium concentration of the red-orange complex of FeSCN2+ is known, the equilibrium concentrations of the reactants (Fe2+ eq and SCN eq) can be calculated, as it si shown below:. Calculate the concentrations of H 2, I 2, and hydrogen iodide (HI) at equilibrium. , often called simply free energy, was named in honor of J. one FeSCN+2, another FeSCN+2 dissociates to become Fe+3 and SCN-. ex: equilibrium expression and numerical value Keq is equilibrium constant. If the reaction was heated, would you expect that value of the equilibrium constant to increase, decrease, or stay the same. This value is t. 1: The equilibrium constant, assuming a general reaction: aA + bB cC + dD Kc = [[CA]]ac[[DB]]bd; all of the concentration values are the concentrations at equilibrium. C12-4-04 Solve problems involving equilibrium constants. Agreement is quite good with the data of Burrows et al. 00200 M KSCN are added to 4. Use the equilibrium concentrations of the reactants and product to calculate equilibrium constants for each of the six trials. Solubility is defined as the upper limit of solute that can be dissolved in a given amount of solvent at equilibrium. 200 M Fe(NO3)3, and for the equilibrium solutions, 0. When the test tube is placed in an ice bath, the low temperature causes the equilibrium constant of the solution decreases and hence the formation of solid copper(II) nitrate is increases. Question: The decomposition of N 2 O 4(g) to produce NO 2(g) is an endothermic chemical reaction which can be represented by the following chemical equation: N 2 O 4(g) ⇋ 2NO 2(g) At 25°C the value of the equilibrium constant, K c is 4. The equilibrium can be represented as: PCl 5 (g) Ý PCl 3 (g) + Cl 2 (g) (a) Complete the equilibrium constant expression for this reaction. The purpose of this lab is to experimentally determine the equilibrium constant, K c, for the following chemical reaction: When Fe 3+ and SCN-are combined, equilibrium is established between these two ions and the FeSCN 2+ ion. If the limitations involved in the quartz solubility determinations are considered, it is justify. 2 × 10 3 M −1 in 6 M ethylene glycol and to 2. (iii) State and explain the effect of increasing temperature on the equilibrium constant above given that the dissociation of water is an endothermic process. O OH H HO OH K NH3 + CO2-+H CO 2-3N water K. Question What is the value of the equilibrium constant at room temperature for the following reaction? Fe3+(aq) + SCN-(aq) Fe(SCN)2+(aq) Prediction Write the equilibrium expression for this reaction. termine the value of the room temperature equilibrium constant (K c) for the formation of the Fe(SCN)2+ ion. The well-known colorimetric determination of the equilibrium constant of the iron(III)−thiocyanate complex is simplified by preparing solutions in a cuvette. According to the data, the calculated equilibrium constant of the bromothymol blue indicator was (1. [53] to obtain the equilibrium constant. 3-5 the thermodynamics of a chemical reaction are completely characterized by measuring the equilibrium constant as a function of temperature; the reaction ∆G, ∆H, and ∆S are all determined. Choose option #2 "CONTINUOUS TEMPERATURE SENSING" from the thermistor menu. Later, you will prepare an equilibrium solution at a temperature near 100 °C and measure the new value of the equilibrium constant. Solubility is defined as the upper limit of solute that can be dissolved in a given amount of solvent at equilibrium. The frequency of breakdown to products is ν‡ and has a numerical value of 6. reaction is quantified by its equilibrium constant. The value of the equilibrium constant, Kc, at a certain temperature is 2. (1) Using pressure as our variable and treating the species as ideal gases, we can write the equilibrium constant as K(T) = P P NO 2 N O 2 2 4. The new constant is the solubility product constant, Ksp. Because FeSCN 2+ is a colored complex, it absorbs visible. [11] and the room temperature data of Tuazon et al. The equilibrium constant will be calculated without correcting for these interactions. Because H 2 O is the only non-condensed phase present, the equilibrium constant is P(H 2 O) 3 = (. The value of K is constant for a reaction at a specific temperature (K is temperature dependent). For your first trial, after preparing the sample as described in the lab manual, the absorbance of tube #1 is 0. Solubility of KHT and Common ion Effect v010714 You are encouraged to carefully read the following sections in Tro (2nd ed. K= [FeSCN2+] [Fe3+] 6 After about 10 minutes, compare them with the solution at room temperature. 1: Temperature dependence of the cell voltage of a copper-silver-cell Using the temperature coefficient calculated from the plot ∂U 0/∂T = - 0. In this experiment you will determine the equilibrium constant for the following reaction: (Spectator ions are not shown. Worksheet #8 Equilibrium Calculations Solve each problem and show all of your work. The SI unit of temperature is the kelvin, and 1 kelvin (K) is defined as 1/273. This will be the temperature for the equilibrium in Equation 1. The subscript eq on the equilibrium contant means that it is defined in terms. Theory: Colorimetric methods of analysis are usually applied to the determination of small concentrations of either inorganic or organic materials in a solution. asked by Chemistry on October 2, 2013; chemistry. 430 Reference Solution #5 1. Learn vocabulary, terms, and more with flashcards, games, and other study tools. of the products and reactants at equilibrium. 8 kcal / mol Yes, expect the reaction to proceed at room temperature because Ea = A < 22 kcal /mol At equilibrium, expect products : reactants ratio = Keq ~ 100:1 10x Keq ~ 1. 1156 kJ mol-1 K-1. The study of Diels-Alder reaction kinetics is extensively. Using Spectrophotometric Methods to Determine an Equilibrium Constant Introduction Chemical reactions do not typically go to completion. Oppositely, the level of solid copper(II) nitrate is increases at the 0. K a is commonly expressed in units of mol/L. 75% higher than the literature value (3. In Part A of this experiment, you will prepare FeSCN 2+ solutions of known concentrations, measure their absorbances at 470 nm, and produce a calibration curve. Chemical reactions may be envisioned in terms of reactants and products and written in the general form. 755 x 10-4 at 291. ); If one reactant is added in extreme excess, the reaction will approach. Calculate the value of the equilibrium constant. A variance of less than Dn= ±0. It is really important to write down the equilibrium reaction whenever you talk about an equilibrium constant. The temperature of 25oC (298. The slope of the plot of. solubility of calcium hydroxide decreases with increasing temperatures. Explain how this might be possible. , the ester will react with water to form a carboxylic acid and an alcohol). In this experiment the temperature of the mixture is constant so the value of the equilibrium constant, K, is unchanged. The equilibrium reaction has a very high Kc. 2 * 104 at room temperature. Set up an ICE table to show the initial, change and equilibri um concentrations of all species in the solution of Part B, step 2. C12-4-04 Solve problems involving equilibrium constants. In Part 1, a series of reference solutions containing the product ion, iron (III) thiocyanate (FeSCN2+), is prepared. Using these values, determine the degree of dissociation and the equilibrium constant, K p, ΔGo and ΔSo for the dissociation at each temperature. 4 10–18NO(g) + 1 Br2(g) NOBr(g) Kc = 1. Use the equilibrium concentrations to calculate equilibrium constants for each of the six trials. equilibrium constant cannot be accurately calculated by considering steric energies of each conformer. (c) On addition of catalyst the equilibrium constant value is not affected. Comparison of the value of the stepwise equilibrium constant (beta(0)) at room temperature for the first chloride complex (n = 1) agrees with literature data. The equilibrium constant decreases from 9 × 10 5 M ‐1 in aqueous phosphate buffer to 5. Start studying Determination of an Equilibrium Constant. Use the value from #1 and the absorbance of the solution (recall A = 2-log %T) to determine the [FeSCN2+] in the other solutions based on their absorbances (including the ones above and below room temperature). Gases dissolve in liquids to form solutions. Example: An example of calculation of the equilibrium constant is: 2SO 2 (g) + O 2 (g) ⇌ 2SO 3 (g) [SO 2] = 0. 512 * These concentrations.
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