[Shadow]

It depends on the capcity of the buffer, but I don't know how to use it.

[Shadow]

The second system is complex equilibria.

[Shadow]

I got that the pH will change to ca. 3.4 for both buffers, meaning that their capacity will be broken.

[Borek]

I am afraid 3.4 is not correct for neither solution. Show how you got it.

Second problem is not that difficult. What is the initial pH of the ammonium acetate solution? What can you tell about ammonia at this pH? How much is protonated? Is there enough NH₃ to react with the added acid? If not - what does the added acid react with?

[Shadow]

7, ammonia is protonated, acetate reacts with protons in both cases.

[Borek]

Which is a good starting point to calculate the new pH.

[Archy12345]

I wish I had a pH meter accurate enough to do a decent calibration curve, because I'm very interested to see how this solution would react.

I think that it could have some pH change resisting qualities, but as far as it meeting the criteria for the definition of a buffer, no it's not a buffer.