Final answer:
Calculating the pH during a titration requires understanding the neutralization of the weak acid by the strong base and using the dissociation constant of the weak acid to find the hydronium ion concentration. The process changes at the equivalence point, after which excess base dictates the pH.
Step-by-step explanation:
The question involves calculating the pH during the titration of a weak acid with a strong base. In this specific case, the weak acid is butanoic acid, and the strong base is NaOH. To calculate the pH after a certain volume of NaOH has been added, you need to consider the neutralization reaction that occurs and the dissociation constant (Ka) of the weak acid.
During the titration before the equivalence point is reached, the weak acid partially dissociates, and the strong base reacts completely with the weak acid to form its conjugate base (the acetate ion). As more base is added, the reaction continues until all the weak acid has been converted to the conjugate base. The pH at any point can be determined by calculating the concentrations of the remaining weak acid, the conjugate base, and the hydronium ion, and then utilizing the formula pH = -log[H3O+].
At the equivalence point, the number of moles of weak acid equals the number of moles of the strong base added. After the equivalence point, the solution contains excess strong base, and the pH can be calculated by determining the concentration of the hydroxide ion (OH-) and using the formula pOH = -log[OH-], and subsequently, pH = 14 - pOH.