Quote essential parts or summaries of links you provide, as questions should be self-contained even in cases the links stop working. Also, users should be able to evaluate the question even without following the links that should serve just for more details or reference.

It is unclear what resources you have consulted before asking this question and what conclusion you have made from that.

Different ingredients and their ratio with different procedures lead to different results. If you want details, you need to ask producers.

Consider formatting guides for texts and formulas/equations/expressions

@FusRoDah My prior comments were not aware of later edit, involving explicit exposure to air. I do not deny the major CO2 influence. The comments pointed out the fact measured pH rarely fits calculated ones and CO2 absorption creates ionic strength forming ammonium and (hydrogen)carbonate.

I have not said it is, once it switches to molar concentrations.

@FusRoDah Not really. it is more about being constant than unity. Any parameter being constant enough can be implicitly involved. OTOH, a parameter being about 1, but not constant enough, cannot.

Well, due CO2, the activity coefficients would get even lower.

One of reasons is your theoretical pH prediction worked with approximation that molar concentrations are numerically equal to thermodynamic activity. // You did not provide the volume of titrated ammonia solution (not ammonium hydroxide solution, as hydroxide neutralises ammonium).

I assume it would be the formation entropy as the entropy difference for the formal change H+ to H+, Similarly as O2 has formation entropy/enthalpy/Gibbs energy as S/H/G changes conventionally zero, for the change O2 to O2.

[Zn(H2O)6]^2+ + [Zn(OH)4(H2O)2]^2- -> 2 [Zn(OH)2(H2O)4], with the product condensation and coagulation.

Negative rate means the negative net rate of the reaction in forward sense and positive net rate in backward sense. But the rates of forward and backward reactions are never negative.