The equilibrium constant for the reaction
AuBr4- + 2Au(s) + 2Br- <--> 3AuBr2-
can be determined by preparing a solution of AuBr4- and AuBr2- in contact with a piece of gold metal. The absorbance of the solution due to AuBr4- is measured at 382 nm. In one experiment, a solution containing a total of 6.41 x10-4 mol/L of dissolved gold (both AuBr4-, AuBr2-) in .4 M of hydrobromic acid was at equilibrium in the presence of gold metal. The total absorbance was found to be .445 in a 1.0 cm cell at 382 nm; however, AuBr2- does not absorb at 382 nm.
In a seperate experiment, the absorbance of 8.54x10-5 M solultion containing only AuBr4- (no AuBr2-) in .4 M HBr was determined in a 1.0 cm cell to be .41 at 382 nm.

1. Calculate the equilibrium concentrations of AuBr4- and AuBr2-.
2. Evaluate the equilibrium constant for the reaction.

I dont even really want an answer... what I really need is an explanation explaining what the frick is going on. We never learnt anything like this in class.
Thank you