Question

A 2.00 mL solution of apotransferrin was titrated with soluble iron via the reaction below. It required 163 μL of 1.43 mM ferric nitriloacetate to reach the endpoint.

apotransferrin +2 Fe³⁺ → (Fe³⁺)₂transferrin

The titration was monitored by measuring the absorbance of the dark red iron-transferrin product at a maximum absorption wavelength of 465 nm.

1. At the equivalence point, the slope of the absorbance vs. volume of Fe³⁺ added graph changes abruptly. Why does this occur?
2. What is the concentration, in mol/L, of the apotransferrin in the original solution?

Answer 1