If I have an excess of sodium carbonate and add sulfuric acid to it, which of the following reaction takes place having in count that there is an excess of sodium carbonate?:
1. 2Na2CO3 + H2SO4 --> 2NaHCO3- + Na2SO4 (before the firts equivalente point)
and 2NaHCO3- + H2SO4 --> 2H2CO3 + Na2SO4 (after the firts equivalente point)
2. Na2CO3 + H2SO4 ---> Na2SO4 + H2CO3
This is without having in count that the final products are Na2SO4 + CO2 + H2O because of the descomposition of the carbonic acid.
Look up a classic inorganic Chem text. The products are pH dependent and in equilibrium with dissolved CO2.
Support the view of Dr P Milham and this is present in any of basic inorganic chemistry books.
It seems advisable to purge (stripping) the titrated solution from dissolved CO2 by sparging N2. The endpoint for the titration of a Na2CO3 aq. with H2SO4 aq. is not expected to be perfectly neutral. For purged titrated solution, is the pH of (pure) Na2SO4 aq. solution.
About predicting the pH of (pure) H2SO4 aq. solutions. ― cf. my posts at: https://www.researchgate.net/post/Do-you-know-a-method-for-titration-of-HNO3-H2SO4-mixtures
About predicting the pH of (pure) Na2SO4 aq. solutions; see: https://www.researchgate.net/post/What_do_you_call_the_electrolyte_of_sodium_sulfate_a_base_an_acid_or_neutral