Description Question #1. The wavelength of maximum absorbance from the absorption spectrum for [Fe( ...
Description Question #1. The wavelength of maximum absorbance from the absorption spectrum for [Fe(SCN)]2+ is: ?max = Question #2. Insert a screenshot of your?absorption spectrum showing your??max? determination here. Question #3.Record the actual volumes of reagents used to prepare Standard Solutions 1 – 4 in Report Table 1. Report Table 1. Reagent volumes used to prepare standard solutions. Standard Solution volume of 0.200 M Fe(NO3)3, mL volume of 0.00200 M KSCN, mL 1 2 3 4 Calculation #1. Calculate the concentration of [Fe(SCN)]2+ in Standard Solution 1, assuming that the SCN– is the limiting reagent. Show your work, including units, below. Enter your calculation result in Report Table 2 below. Question #4. Calculate the concentration of [Fe(SCN)]2+ in Standard Solutions 2 – 4 and enter the results in Report Table 2 below. Also enter the absorbance data measured for Standard Solutions 1 – 4 in Report Table 2 below. Include the wavelength at which you made the measurement. Report Table 2. Absorbance and Concentration of Standard Solutions 1-4. Standard Solution [[Fe(SCN)]2+], M Absorbance at _________ nm 1 2 3 4 Question #5. Insert a screen shot of your calibration plot (standard curve) including the slope, y-intercept, and R2 (correlation) values. Label your axes. Question #6. Complete Report Table 3 below using the actual volumes used to prepare the equilibrium mixtures. Record the volumes to 2 decimal places. Report Table 3. Initial Concentrations of Equilibrium Mixtures A – E. Equilibrium Mixture Fe(NO3)3, mL (________ M) KSCN, mL (________ M) total volume of mixture (mL) A B C D E Question #7. Record the absorbance of each of the equilibrium mixtures in Report Table 4. Note the wavelength used for the measurements. Report Table 4. Absorbances of equilibrium mixtures. Equilibrium Mixture Absorbance at ___________ nm A B C D E DATA ANALYSIS Calculate Concentrations in Equilibrium Mixtures A-E Calculation #2. Calculate the initial concentrations of Fe3+ and SCN– in Equilibrium Mixture A. Show your work, including units, below. Also enter your calculation result in Report Table 5 below. Question #8. Calculate the initial concentrations of Fe3+ and SCN– in Equilibrium Mixtures B – E. Enter your calculation result in Report Table 5 below. Report Table 5. Initial Concentrations of Equilibrium Mixtures A – E Equilibrium Mixture initial Fe3+ (M) initial SCN– (M) A B C D E Calculation #3. Calculate the equilibrium concentration of [Fe(SCN)]2+ in Equilibrium Mixture A by using the absorbance measured for the mixture and the best-fit line from the calibration plot. Show your work, including units, below. Also enter your calculation result in Report Table 6 below. Calculation #4. Calculate the equilibrium concentrations of Fe3+ and SCN– in Equilibrium Mixture A using an ICE table. Show your work, including units, below. Also enter your calculation result in Report Table 6 below. Calculation #5. Calculate the value of the equilibrium constant, K, for Equilibrium Mixture A, by using the equilibrium concentrations of each of the three species in the equilibrium system. Show your work, including units, below. Also enter your calculation result in Report Table 6 below. Question #9. Calculate the equilibrium concentrations of [Fe(SCN)]2+ in the mixtures B – E. (You may use a spreadsheet for these calculations if you wish.) Calculate the equilibrium concentrations of Fe3+ and SCN– of Equilibrium Mixtures A – E, using an ICE table. Calculate a value for the equilibrium constant, K, for each mixture (i.e., by using the equilibrium concentrations of each of the three species in the equilibrium system). Enter your calculation results in Report Table 6 below. Report Table 6. Absorbances, Equilibrium Concentrations, and Values of the Equilibrium Constant for Equilibrium Mixtures A – E Equilibrium Mixture equilibrium [[Fe(SCN)2+]], M equilibrium [Fe3+], M equilibrium [SCN–], M equilibrium constant, K A B C D E RESULTS Calculation #6. Calculate an average value for the equilibrium constant, Kave, and the standard deviation (by using the function =stdev.p(range of K values) in Excel). Values of K can be considered constant if each K value differs from the average by less than 2 times the standard deviation. Average K = _________________ Standard deviation = ___________________ Question #10. Comment on the K values you obtained in this experiment. Can the values you obtained for K be considered constant, according to the criteria (e.g., standard deviation) described above? Support your claim using evidence (i.e., experimental data or results). Are your results consistent with what you’ve learned about equilibrium? Explain your reasoning.
