Question

Suppose that you are given the task of determining the SCN- content of a blood sample by forming the Fe(SCN)2+ complex and measuring the absorbance. You begin by taking a 10.0-mL volume of the blood sample, centrifuging it, transferring 3.0 mL of the clear serum to a flask, and then adding 17.0 mL of 0.20M Fe3+. The %T of this solution, measured at 460 nm in a 1.0-cm diameter cuvet, is 75%. A calibration curve, prepared from Fe(SCN)2+ standards, indicates that the Fe(SCN)2+ concentration of the diluted sample solution is 0.24 mM. Calculate the SCN- content (in mM) of the original blood sample.
(Atomic weight of Fe = 55.85 g/m; formula weight of SCN- = 58.08 g/m)
A) 0.036 mM D) 1.36 mM
B) 0.24 mM E) 1.60 mM
C) 0.48 mM

Answer 1