[cheemiistryyyy]

Hi everyone,

It concerns the following task (see attachment), which also includes solutions. What I can't comprehend is the diagram. I don't understand how to interpret this diagram and why it looks the way it does. Since we haven't discussed this topic yet and I'm studying ahead, I'm having difficulty understanding what the diagram represents. Could someone please explain this diagram to me step by step so that I can understand it?

the following task:
Calculate and sketch the Pourbaix diagram based on the following reactions and label the individual phases. Note: Plot the curve for reaction c) from the intersection point of reactions a) and b).
Why are there deviations from the Pourbaix diagram observed in the experiment?

[Borek]

Have you tried to google for Pourbaix diagram and read what and how it represents? Even wikipedia should give you some basic information.

[cheemiistryyyy]

I have that, but it's not just about the basic information, it's about the relationship of the diagram with the task.
I'm not sure what I need to do exactly.
Especially, I don't understand the following: Plot the curve for reaction c) from the intersection point of reactions a) and b). What should I do here?

[Borek]

OK, I see what you mean.

My bet is that the Zn diagram is given just as an example and is not directly related to the problem.

Haven't worked with Pourbaix diagrams in ages, so I can be missing something, but first reaction is not pH dependent - so it will produce just a horizontal line on the diagram.

Second reaction is not potential dependent, so it will produce a vertical line.

Thermodynamic data should be probably enough to calculate the slope for the reaction c, and it must go through the point of intersection for the a and b reactions. I admit I am guessing here.

[Corribus]

It seems the problem wants you to sketch a diagram (similar to that provided for Zn) for the generic metal Me using the equations and data provided. I.e., at what pH and potential values are the boundaries between Me, MeO2, MeOH2 etc.