In article
>,
Madalch > wrote:

> On Jan 11, 12:10*pm, Wildbilly > wrote:
> > In article
> > >,
> >
> > *Madalch > wrote:
> > > It's not 7 because you're neutralizing weak acids (acetic, tartaric,
> > > etc) with a strong base.
> >
> > It's the isoelectric point of tartaric acid, where it isn't an ion, but
> > still has both of its "acidic" protons attached.
>
> No it isn't. Tartaric acid will have both of its acidic protons
> attached at a low pH; when you react it with sodium hydroxide in the
> titration, you're removing both of the acidic hydrogens.
>
> Isoelectric points, as the link you provide indicates, are only
> relevant for amphoteric substances, such as metal oxides or amino
> acids. Tartaric acid is not amphoteric.
>
> If you titrate a strong acid HX with sodium hydroxide, then at the
> equivalence point, all the acid will be converted to X-. Since HX is
> a strong acid, X- is a very weak base, and will not affect the pH of
> the solution. So the solution is neutral.
>
> If you titrate a weak acid HA with sodium hydroxide, then at the
> equivalence point, all the acid will be converted to A-, which is a
> weak base. The A- anion will react with water via the reaction: A- +
> H2O <==> HA + OH-. This means that there is a small amount of OH- in
> solution, and the solution is basic.

My bad, you're right.
--
³When you give food to the poor, they call you a saint. When you ask why the poor have no food, they call you a communist.²
-Archbishop Helder Camara

http://www.jpost.com/servlet/Satelli...cle%2FShowFull
http://countercurrents.org/roberts020709.htm