The concentration of FeCl₂ in an aqueous solution was determined by redox titration with K₂Cr₂O₇. The sample was first dissolved in HCl to make the solution acidic. The working reaction is shown below:

Cr₂O₇^2–(aq) + 6 Fe²⁺(aq) + 14 H⁺(aq) → 2 Cr³⁺(aq) + 6 Fe³⁺(aq) + 7 H₂O(l)

In the diagram below, the Cr₂O₇^2– ions are depicted in green spheres and Fe²⁺ ions are depicted in orange spheres. In the buret, the concentration of Cr₂O₇^2– ions is 0.170 M. The volumes in the buret and the flask are the same. Calculate the concentration of the FeCl₂ in the solution and determine the percentage of the Cr₂O₇^2– that must be added in order to react with all the Fe²⁺ ions.