Titration curve of an acid and it's conjugate base

[September24]

Does anyone have a graph that overlays an acid getting titrated with a strong base with the graph of the acid's conjugate base being titrated with a strong acid.


Basically, I just want to know what portion of the graph do they share? I've written down for some reason that both graphs will have same "1/2 equivalence point". At this point, ph=pka or ph=pkb. But since pka=14-pkb, how can they be the same? Or did I mean that they will be at the same point along the X axis. They will require that the same amount of titrant but will be at different ph.

What else should they share? My guess would be the equivalence point.

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[chenzt]

Does anyone have a graph that overlays an acid getting titrated with a strong base with the graph of the acid's conjugate base being titrated with a strong acid.


Basically, I just want to know what portion of the graph do they share? I've written down for some reason that both graphs will have same "1/2 equivalence point". At this point, ph=pka or ph=pkb. But since pka=14-pkb, how can they be the same? Or did I mean that they will be at the same point along the X axis. They will require that the same amount of titrant but will be at different ph.

What else should they share? My guess would be the equivalence point.

to get to half way to equivalence point, the acid and conjugate base will require the same amount of titrant if they have the same concentration. (actually any monoprotic acid/base of the same concentration will work - concentration is the key here, not the type of acid). At that point, pH = pKa because of henderson hasselbach, which states pH=pKa + log (A-/HA). at halfway point, theres a 50/50 ratio of A- and HA, so the log of 1 becomes 0, and pH simply equals pKa. So yes, they are the the same along the x-axis.

 

[ipmed]

I don't think ph=pkb at half eq. Point because hh still says that ph=pka. Correct me if Iam wrong

 

[chenzt]

I don't think ph=pkb at half eq. Point because hh still says that ph=pka. Correct me if Iam wrong

ah yes, pOH = pKb. I automatically switch over the base scale when talking about base.