Question

Based on an acid/base titration, is it possible to determine whether or not an unknown acid is mono/di/triprotic? why or why not? Is it possible to identify the chemical formula of your unknown acid just from your titrations? Why or why not?

Answer 1

Every titration has an equivalence point, corresponding to the precise point of complete consumption of the analyte. In case of acid/base titration, the number of distinct equivalence points achieved during titration will give the information about the proticity of the acid.

For acquiring such an information however, acid/base titrations carried out by conductometry or based on the pH are to be carried out. In such titrations, a plot of change in conductance or pH per unit volume of titrant versus the volume of titrant will give sigmoid curves with the equivalence point being the volume of titrant at which there occurs a steep increase in change in conductance per unit volume of titrant. If the acid given is monoprotic, there will be one equivalence point and if there are two or three such points, the acid given is di/tri-protic. Unfortunately, conventional volumetric titrations carried out using visual-aiding indicators are obsolete for this purpose.

From the proticity of the acid given, one can only identify the chemical formula of the acid in terms of H_nA where n is the proticity of the acid and A is its conjugate base. Due to the absence of data on its molecular mass and elemental composition of the acid/conjugate base which are vital, it is impossible to determine the precise chemical formula of the acid merely by titrations.