[burntcookie]

Hi,

I'm answering some questions for a lab write-up and I'm stuck. One of the things we had to do was dissolve two samples of iron ore in HCl, measure their initial potentials and use that to calculate their Fe(III)/Fe(II) ratios, and then compare them. I'm not sure how to answer the following question:

Discuss the reliability of the Fe(III)/Fe(II) ratio in terms of accuracy and precision. Usually it is not good, why? (Hint: what effect might be considered in the potentiometric titration of an ore?). Most students find that the ratio is higher in their second sample. Why?

I'm thinking that maybe it has something to do with the Fe(II) being readily oxidized in the presence of oxygen...am I on the right track?

[Borek]

What can oxidize Fe(II) to Fe(III)?