(Use the In-lab observations to complete the laboratory report. Turn in to your
ID: 488805 • Letter: #
Question
(Use the In-lab observations to complete the laboratory report. Turn in to your instructor when you have completed the report.) for Trial 1. Conc. Fe (NO_3)_3 soln. used _____ M Conc. KSCN soln. used _____ M for Trial 1. for Trial 1. for Trial 1. (What errors may have occurred during the performance of this experiment and altered your results? Use an additional page, if necessary.) (Turn in to your Instructor with the post laboratory report for this experiment.) What would have happened to your % Transmittance reading and to your calculations of K_eq if the spectrophotometer had been set at 520 nm rather than 447 nm? (Clearly explain your reasoning.) How would your calculations of the concentration of [FeSCN]^2+ been affected if the cuvette you used had a 1.5 cm path length rather than the 1.0 cm value you were told to use? (Clearly explain your reasoning.) Would your K_eq results have been affected if you had chosen to use 5.00 mL of KSCN and altered the volume of Fe(NO_3)_3 solution used? (Explain clearly.) The equilibrium constant you studied in this reaction is dependent upon the [H^+]. What was the effect upon the magnitude of K_eq caused by using dilute HNO_3 rather than 1.0 M HNO_3? (Would this change your answer to Question 3?) Fe^3+ + HSCN doubleheadarrow [FeSCN]^2+ + H^+ K_eq = [FeSCN]^2+ [H^+]/[Fe^3+][HSCN]Explanation / Answer
Post lab questions
1. If lambda-max value is set at a different value, the %transmittance value would be much higher, that is the absorbance would be lower than the calculated value.
2. If cuvette is 1.5 cm instead of 1.0 cm, the concentratin of [FeSCN]2+ would be lower than the value calculated here as,
concentration = absorbance/path length x molar absorptivity
3. In the reaction, SCN- is the limiting reagent. If instead Fe3+ is the limiting reagent, the concentration of [FeSCN]2+ would be dependent upon the concentration of Fe3+ and not on SCN- present.
4. The Keq constant would decrease If dilute HNO3 is used in place of concentrated HNO3 solution. Keq is directly proportional to H+ ion present in solution.
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