[BioMajor]

I did an experiment last week and need to write a net ionic equation for the titration of NaOH and H₃PO₄ at its first equivalence point. I am getting 3OH^-(aq)+3H⁺<--->3H₂O(l), but I know this isn't right? I'm not exactly sure what I'm doing wrong? My starting reaction that I have is 3NaOH(aq) + H₃PO₄(aq)<------> Na₃PO₄(aq) + 3H₂O (l).

Thank you for any advice!

[tamim83]

Phosphoric acid is a weak electrolyte so you cannot dissociate it into ions.

Hope that helps some. 

[BioMajor]

Oh wow, now I feel stupid, lol. I don't know why I wasn't thinking about that. Lack of sleep may have something to do with it, lol.

I do have another question though. I have seen some people completing this reaction as I did, but some have it as NaOH (aq) + H₃PO₄(aq)----> NaH₂PO₄(aq) + H2O(l). Is this what I should be using, as it is for the first equivalence point? I'm not sure why acid/base reactions still confuse me... I just don't seem to understand this?


Thank you!

[tamim83]

NaOH (aq) + H3PO4(aq)----> NaH2PO4(aq) + H2O(l)

This is the equation for the first equivalence point.  The other equation you had (with the "3NaOH...") is used if you added enough NaOH to remove all of the protons at once, which wouldn't happen in a titration. 

[BioMajor]

Ok, thanks! I've got it now!