posted by Hannah .
For the reaction that occurs in the voltaic cell,
I don't understand how the Pt(s) would be used to solve this question.
Thanks for explaining what you don't understand. It makes it easier. The Pt is an inert electrode. Obviously you can't make electrodes of Cr^+3 and/or Cr^+2 (as you can with iron meta); therefore, an inert electrode is used for electrical contact. Otherwise, the Nernst equation is used to calculate Eo of the cell.