Question

Conclusion about Potentiometric Methods for a Weak Base

Answer 1

Conclusion:

Analysis showed that the measured pH of the three conditioners has slight deviations to the calculated pH when the potentials of the buffer solutions are considered.

Percent Errors of the pH are the following: 0 .538°/o for L'Oreal, - 1,285°/o for Palmolive and 0.262°/o for Pantene conditioner.

Errors may be accounted from personal errors due to the preparation of the solutions . Since the conditioners are emulsions, they are not that very soluble in water which causes unconformities in the reading of the glass electrode.

After the analysis has been conducted,the volume of the titrant at endpoint was found to be 20.20 ml. It was observed when the first derivative (change in pH over change in volume) was plotted.The sudden rise on the plot indicates the endpoint.

Calculating for the acid dissociation constant,(kb),the idea of titrating a weak monoprotic base with a strong acid was used. At half -equivalence point,which is 10.1O m , the pH is equal to -logkb . Considering that relationship,the computed base dissociation constant is 1.95 x 10-5 .

The true value of kb . W ith this the computed relative error is

11.43 °/o. Errors can be caused by personal and random errors during the preparation of the solution for the standardization of the base and during the titration.