Final answer:
To calculate the pH during a titration, we must consider the amount of acid and base present, and whether the reaction is before, at, or after the equivalence point. Using principles of acid-base chemistry, including the Henderson-Hasselbalch equation and the pH = -log[H+] formula, we can determine the pH at different stages of the titration.
Step-by-step explanation:
Calculating pH During a Titration Process
To calculate the pH of the titration solution after the addition of specific volumes of NaOH titrant, we can follow these steps:
- Determine the moles of the acid and base.
- Calculate the remaining concentration of the acid or base that is in excess.
- Use the relevant chemical equations and constants to determine the pH.
For example, if no NaOH has been added, the pH is simply that of the acetic acid solution. When NaOH is added, we need to check if the reaction has gone to completion and whether there is excess NaOH or acetic acid. At half-neutralization, the pH can be found using the Henderson-Hasselbalch equation. After the equivalence point, the excess NaOH will determine the pH.
Before the equivalence point, determine the moles of HCl and NaOH, then calculate the number of moles of HCl that remain. Use this to find the concentration of H+ ions and then calculate the pH using the formula pH = -log[H+].
At the equivalence point, the moles of HCl will equal the moles of NaOH added. For a strong acid with a strong base, the pH will be neutral, around 7.00.
Beyond the equivalence point, there will be excess NaOH in the solution, and its concentration can be used to determine the pOH, and thus the pH of the solution (pH = 14 - pOH).