Chemistry Lab Report Paper Assignment help

Chemistry Lab Report Paper Assignment help

 
Group Portion



You now have the information you will need to calculate Kc for the Fe3+, SCN–, FeSCN2+



equilibrium. To calculate K, you must determine the equilibrium concentrations of all three species. Remember that “I.C.E.” tables (Initial concentration, Change in concentration, Equilibrium concentration) are useful for accounting for the information necessary for calculating equilibrium constants. Prepare an “I.C.E.” table for solution 6 according to the following example, read the hint below, and follow steps (a) – (h) below which will lead through the calculations needed to fill in each of your I.C.E. tables.







0.000111426  











0.00038858  











0.00013858  











0.000111426  











0.000111426  











0.000111426  











0  











0.0005  











0.00025  











a. Show how to calculate the initial concentrations of Fe3+ and SCN− in solution 6. Then enter those concentrations in the first two cells of the table (row I). 



b. Determine the initial FeSCN2+ concentration that should be entered into the  I.C.E. table. (Hint: At this “initial point”, has the reaction occurred yet?)



c. What was the equilibrium FeSCN2+ concentration determined by spectrophotometry for solution 6? Enter this value into your I.C.E. table.



d. By comparing the initial and equilibrium concentrations of FeSCN2+, determine what value should go into the change row for FeSCN2+. 



e. Now use the change in FeSCN2+ to find the changes for Fe3+ and SCN−, and enter those values in the appropriate cells of the table. Pay careful attention to the signs here and consider the change in concentration of a product (FeSCN2+ in this experiment) should compare to the change in concentrations of reactants (Fe3+ and SCN−).



f. Complete the columns under Fe3+ and SCN− by using the initial concentrations and concentration changes to find the equilibrium concentrations.



g. Write the mathematical expression for the equilibrium constant in terms of the concentrations of Fe3+, SCN–, and FeSCN2+. Note that the generic reaction from the prelab quiz has the same stoichiometry as this reaction.



h. Using the mathematical expression for the equilibrium constant and the equilibrium concentrations of Fe3+, SCN–, and FeSCN2+ from the “E” row of the I.C.E. table, calculate K for this solution. (Show your work.)



individual Portion



1. Explain why solutions 0–5 were prepared with such a large concentration of SCN− (1 M), but solutions 6–10 were prepared with an SCN− concentration closer to that of the Fe3+. Consider what the two sets of solutions were used for in the experiment.



2. Given which experimental conditions were varied in testing sample solutions 6–10, should you expect a wide range of K values or a small range about a single value? Explain your answer.



3. What other experimental condition could have been changed (which were not in this experiment) that would be expected to change the value of K for this reaction?



4. What color light is 470 nm, and why do solutions containing FeSCN2+(aq) appear red if it absorbs light mostly around 470 nm?