Answer to Question #72679 in Chemistry for Tony

Question

This is a question about analytical chemistry, in which concentration of [Fe(SCN)]2+ is determined by measuring the light absorbance after adding excess Fe 3+ ions into a sodium thiocyanate solution. However, I am so confused since the yellow color of the iron 3+ ions will affect the color intensity of the solution. Will it affect the measurement of the blood red colored [Fe(SCN)]2+ solution concentration?

Answer 1

The essence of this analysis is estimating [Fe(SCN)]2+ concentration while comparing measured absorbance
with absorbance of the standard solution with known concentration. Therefore, yes adding some more Fe3+
will affect the color, but this will be reflected in the measurement results.