I am not familiar with this area of chemistry. The theory given in the manual doesnt really help. The only thing it says is that absorption is proportional to concentration. Maybe you can give me some assistance on how to get started and some equations that i can use.(adsbygoogle = window.adsbygoogle || []).push({});

The eqilibrium constant for: [tex]AuBr_{4}^{-} + 2Au + 2Br^{-} --> 3AuBr_{2}^{-}[/tex] can be determined by preparing a solution of AuBr[tex]_{4}^{-}[/tex] and AuBr[tex]_{2}^{-}[/tex] in contact with a piece of gold metal.

In one experiment a solution initially containing [tex]6.41x10^{-4}[/tex] mol/L of dissolved gold (both AuBr[tex]_{4}^{-}[/tex] and AuBr[tex]_{2}^{-}[/tex]) in 0.4 M HBr was allowed to attain equilibrium in the presence of gold metal. The absorbance was 0.445 in a 1.00 cm cell at 382nm.

In a separate experiment, the absorbance of a [tex]8.54x10^{-5}[/tex]M solution of only AuBr[tex]_{4}^{-}[/tex] (no AuBr[tex]_{2}^{-}[/tex] ) in 0.4 M HBr was determined in a 1.00cm cell to be 0.410 at 382nm. (AuBr[tex]_{2}^{-}[/tex] does not absorb at 382nm.)

a) calculate the equilibrium concentrations and b) evaluate the equilibrium constant.

I can get b) if i knew how to do a) can someone help me with this one?

Thanks

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# Spectrophotometry area of chemistry

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