Ore is a naturally occuring rock found in Earth's crust that contains valuable minerals and metals.  In an experiment, a researcher dissolved a sample of ore containing an unknown amount of iron in HCl(aq).  The resulting aqueous solution, which contained both Fe2+(aq) and Fe3+(aq), was poured through a Jones reductor column containing Zn(Hg)(s) to convert all iron ions into a single oxidation state.  The conversion of Fe3+(aq) to Fe2+(aq) in the Jones reductor column is shown in Figure 1.Figure 1  Jones reductor column used for the conversion of Fe3+(aq) to Fe2+(aq).  The resulting Fe2+(aq) solution was collected using a syringe.To determine the total amount of iron in the sample, the Fe2+(aq) solution was then transferred to a container and titrated with 0.1 M K2Cr2O7(aq), which resulted in the conversion of Fe2+(aq) to Fe3+(aq) in an irreversible process.  A reference electrode was used to monitor the solution potential as a function of K2Cr2O7(aq) volume added, and the equivalence point of the solution was reached after the addition of 9.50 mL of K2Cr2O7(aq).  A schematic of the experimental setup is shown in Figure 2.Figure 2  Experimental setup for the titration of Fe2+(aq) with K2Cr2O7(aq) under acidic conditionsIn a second experiment, the researcher prepared another sample of Fe2+(aq) but used a 0.1 M I3−(aq) titrant solution instead of K2Cr2O7(aq).The standard reduction potentials for the species involved in the experiments are given in Table 1.Table 1  Standard reduction potentialsReduction half-reaction E°(V)Cr2O72−(aq) + 14 H+(aq) + 6 e− → 2 Cr3+(aq) + 7 H2O(l) +1.33Fe3+(aq) + e− → Fe2+(aq) +0.76I3−(aq) + 2 e− → 3 I−(aq) +0.53Zn2+(aq) + Hg(l) + 2 e− → Zn(Hg)(s) −0.76 Question 28What happens to the chromium atoms in K2Cr2O7(aq) during the titration in the passage?A.Cr6+ is oxidized to Cr3+B.Cr7+ is oxidized to Cr3+C.Cr6+ is reduced to Cr3+D.Cr7+ is reduced to Cr3+