[raafiki]

Okay so I cant figure out how to write out the half reaction for this:
Cu / Cu^2+ (0.00680 M) // Cr^3+ (0.830 M), Cr2O7^2- (0.0550), H^1+ (1.00 M) / Au

Cu is easy,
Cu -> Cu2+ +2e-

but can some one explain how you would write it for Cr3+, Cr2O7^2-?
And Au is a passive electrode btw.

I eventually need to find the E cell potential but i just needed help getting started...