Equivalence Point Calculation: Joe's Question

[josephcollins]

Hi ppl, I was wondering. I have found the Equivalence point from the graph of volume versus pH for a given titration. To determine the Half equivalence point for to calculate Pka=Ph, do I half the pH or the volume which I found for the Equivalence point initially? Thanks for any help, Joe

 

[chem_tr]

Dear friend,

Half equivalence in titrations means that the half mole of total acid or base is neutralized; it is not the half of pH value. Volume may be incorrect, so I recommend that you stick to mole ratios.

 

[ravenprp]

Hi Joe,

Thank you for your question. To determine the half equivalence point, you should halve the volume that you found for the equivalence point initially. This is because the equivalence point is the point at which the number of moles of acid and base are equal, while the half equivalence point is the point at which half of the acid has been neutralized by the base.

To calculate pKa, you can use the Henderson-Hasselbalch equation, which relates the pH of a solution to the pKa of an acid and the concentration of the acid and its conjugate base. You can use the half equivalence point to determine the concentration of the acid and its conjugate base at that point, and then plug those values into the Henderson-Hasselbalch equation to calculate the pKa.

I hope this helps! Let me know if you have any further questions.