Info collected: KSCN (0.003 Molarity): volume dispensed from buret = 1.00 ml Fe(
ID: 588498 • Letter: I
Question
Info collected: KSCN (0.003 Molarity): volume dispensed from buret = 1.00 mlFe(NO3)3 (0.20 Molarity): volume dispensed from buret = 19.00 ml
Absorbancy of the mixture: 0.640 2. In Part 1 of this experiment, you made a mixture with a large excess of Fe and then 120, assumed that the SCN was essentially "used up" in the reaction. Using K follow the steps below to evaluate the validity of this assumption. a) Calculate the moles of SCN- ion that are actually present at equilibrium in the mixture in Part 1. (Hint: use an ICE table and the provided value of K.) b) Calculate the percentage of the SCN ion that did not react in this mixture. This percentage is calculated as follows: moles of SCN-at equilibrium initial moles of SCN % of SCN-not reacted = x100% Based on your calculations above, was it reasonable to assume that essentially all of the SCN reacted with Fe3* in Part 1? Explain. c)
Explanation / Answer
Given data:
The molarity of KSCN solution = 0.003 M
Volume dispensed from buret = 1 mL
Therefore, the no. of mmol of SCN- = 0.003 mmol/mL * 1 mL = 0.003 mmol
The molarity of Fe(NO3)3 solution = 0.2 M
Volume dispensed from buret = 19 mL
Therefore, the no. of mmol of Fe3+ = 0.2 mmol/mL * 19 mL = 3.8 mmol
(a) K = [FeSCN2+] / ([Fe3+] [SCN-])
i.e. 120 = x / {(3.8 - x) * (0.003 - x)}
i.e. x = 0.00299
(b) The % of SCN- not reacted = {(0.00300 - 0.00299) / 0.003} * 100 = 0.333 %
(c) It is not reasonable to assume that essentially all of the SCN- reacts with Fe3+ in part I.