Name Lab Daytime An Equilibrium Constant Pre-Lab Assignment 1. Refer to Table 2,
ID: 1085855 • Letter: N
Question
Name Lab Daytime An Equilibrium Constant Pre-Lab Assignment 1. Refer to Table 2, test solution 3 in the procedure. At equilibrium, the determined to be 1.5x 10 M in 10.0 m total volume of solution. concentration of the FeNCS a. Calculate the number of moles of Fe and SCN added. b. Calculate the number of moles of FeNCS tormed. c. Calculate the number of moles of each reactant present at equilibrium. moles at equilibrium = initial moles-moles used up d. Calculate the concentrations of all species at equilibrium e. Calculate KExplanation / Answer
a) Moles of Fe3+ added = 0.002 x (5/1000) = 0.00001
Moles of SCN- added = 0.002 x (3/1000) = 0.000006
b) Moles of FeNCS+2 formed = 1.5 x 10-4 x (10/1000) = 1.5 x 10-6
c) Moles of Fe3+ present at equilibrium = 0.00001 - 1.5 x 10-6 = 0.0000085
Moles of SCN- present at equilibrium = 0.000006 - 1.5 x 10-6 = 0.0000045
d) [Fe3+] = 0.0000085 / 0.01 = 0.00085 M
[SCN-] = 0.000006 / 0.01 = 0.0006 M
[FeNCS2+] = 1.5 x 10-6 / 0.01 = 1.5 x 10-4 M
e) K = [FeNCS2+] / [Fe3+][SCN-]
K = 1.5 x 10-4 / (0.00085 x 0.0006)
K = 294.118 M-1
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