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## Homework Statement

Give the reactions that take place when the following solutions are passed through a Jones-redactor (amalgamated zinc), and calculate the equilibrium constant at 298.15 K for each.

0.01 mol/dm3 CuCl2

0.01 mol/dm3 CrCl3

0.01 mol/dm3 NH4VO3 (pH =1)

Data:

Couple, E° value

Cu

^{2+}/Cu 0.34

Cr

^{3+}/Cr –0.74

Cu2+/Cu+ 0.16

Cr2+/Cr –0.90

VO

_{2}

^{+}/VO

^{2+}1.00

Zn2+/Zn –0.76

VO

^{2+}/V

^{3+}0.36

TiO

^{2+}/Ti

^{3+}0.10

V3+/V2+ –0.255

Ag+/Ag 0.80

V2+/V –1.13

Fe3+/Fe2+ 0.77

## Homework Equations

The usual equations - ΔG=-nFE, ΔG°=-nFE°, ΔG=-RTln(K).

## The Attempt at a Solution

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So one redox equation going on for all cases is the Zn2+/Zn couple, E°=–0.76, Zn

^{2+}+ 2e

^{-}::equil:: Zn. The forward reaction will occur if E°[Zn

^{2+}/Zn]>E°[Couple

*j*], where

*j*is the couple which represents the redox equation occurring on the other side.

But how do I know which equation

*j*will be, from all the different choices we get for each case? For example, in the first case, is it Cu

^{2+}+ e- -> Cu

^{+}, Cu

^{+}+ e- -> Cu, or Cu

^{2+}+ 2e- -> Cu which we need to consider as couple

*j*against E°[Zn

^{2+}/Zn]? And how do we determine which equation we need to take for all three cases. I have seen the solutions but this question, of which one to choose of the possible equations, is not properly explained.