[plankk]

I have a task, which I can't solve. It is:

Calculate a solubility of BaCO₃ in water wuth taking protolysis under consideration.

I tried to simplify calculation by making identity: [Ba]=[HCO₃]=[OH]=S and after all I gained: and in the key I've got S=3,24*10^-4

Then I attempted by making identity: [Ba]=S=[CO₃]+[HCO₃] and [HCO₃]=[OH] so [CO₃]=S - [OH]. After all I had two quadratic equations and I got S = 1,1*10^-4 so it isn't also a correct answer.

In caluclation I used the constant, which I found in that book, so:
K_so=10^-8,3
K_b1=10^-3,7
K_b2=10^-7,6

Where did I simplify to much?

[Borek]

Galus again?

Don't pay attention to 'concentration of BaSO4(s)', I just had to put some amount of solid into the solution.

These are calculated while solving full system numerically. 1.3e-4 seems to be the correct answer, so your second approach seems to be in the correct ball park.

[plankk]

Yeah Galus. I hate that guy. The most strange fact is that in the exemplary tasks he shows good approach (in my opinion) and after all in the answers you can find such horrible mistakes.

Thanks again.

I checked in my notes: in my second method pH=9,90 so real close.

[Borek]

Galus was editor of the book, chapters, questions and solutions were provided by others.

And I know him in person - he is quite a nice guy