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I have read that Latimer diagrams can be represented both in an acidic medium (pH = 0) and in a basic medium (pH = 14).

I would like to know how to calculate the reduction potentials as a function of pH. That is, if I know the reduction potential for the pair $X^{+}/X$ at pH = 0, calculate it for another pH.

I thought the Nerst equation could be applied, but I'm not sure about that.

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Nernst equation is the only way of solving this problem. Let's consider the example of the reduction of permanganate. The half-reaction is: $$\ce{MnO4- + 8 H+ + 5 e- -> Mn^2+ + 4 H2O}$$

The potential can be written as:

$$E = E^\circ + \frac{0.059}{5}\log \left(\frac{\ce{[MnO4-][H+]^8}}{\ce{[Mn^2+]}} \right)$$

If you want to see explicitly the $\mathrm{pH}$, you can rewrite the preceding expression, which gives:

$$E = E^\circ + 0.012 \log \left(\frac{\ce{[MnO4^-]}}{\ce{[Mn^2+]}}\right) - \left(\frac{8\times 0.059}{5} \right) \mathrm{pH}$$

or : $$E = E^\circ + 0.012 \log \left(\frac{\ce{[MnO4^-]}}{\ce{[Mn^2+]}}\right) - 0.094 \: \mathrm{pH}$$

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  • $\begingroup$ So, for example, what would be the reduction potential at pH = 0? And, another question, if I want to determine the potential for calcium reduction is $\mathrm{Eº(Ca^{2+}/Ca)} = -2.760 V$ under normal conditions. What would it be at pH = 10? Thanks $\endgroup$ – aprendiendo-a-programar Oct 22 at 17:39

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