Problem:
An acidified sample is passed through the reductor, collected, and titrated with a strong oxidizing titrant of known concentration (for example KMnO4). The most common version is the so-called Jones-reductor that contains amalgamated zinc granules.
Give the reactions that take place, and the corresponding equilibrium constants, when the following solutions are passed through a Jones-reductor:
0.01 mol/dm3 CuCl2
0.01 mol/dm3 CrCl3
0.01 mol/dm3 NH4VO3 (pH =1)
Data provided:
E°(Zn2+/Zn) = –0.76
E°(Cu2+/Cu) = 0.34
E°(Cu2+/Cu+) = 0.16
E°(Cr3+/Cr) = –0.74
E°(Cu2+/Cu+) = 0.16
E°(Cr2+/Cr) = –0.90
E°(VO2+/VO2+) = 1.00
E°(V3+/V2+) = –0.255
E°(V2+/V) = –1.13
Comment:
If I could work out what reaction takes place, there is sufficient data for me to easily work out the equilibrium constants for those reactions. So how do I work out which reactions take place?