In the titration of a weak acid with a strong base, the equivalence point is reached when the moles of the weak acid equal the moles of the strong base. At this stage, the weak acid has been completely neutralized, resulting in the formation of its conjugate base. This conjugate base is crucial for determining the pH at the equivalence point.

To calculate the pH at this point, it is essential to recognize that the solution will primarily consist of the conjugate base, which can hydrolyze in water. The hydrolysis reaction can be represented as follows:

\[ \text{A}^- + \text{H}_2\text{O} \rightleftharpoons \text{HA} + \text{OH}^- \]

Here, A^- represents the conjugate base, and HA is the weak acid. The presence of hydroxide ions (OH^-) from this reaction will affect the pH, making it basic.

To find the pH, one can use the equilibrium expression for the hydrolysis of the conjugate base. The base dissociation constant (K_b) can be calculated using the relationship:

\[ K_b = \frac{K_w}{K_a} \]

where K_w is the ion product of water (1.0 x 10^-14 at 25°C) and K_a is the acid dissociation constant of the weak acid.

Additionally, the equivalence volume of the titrant can be determined using the equation:

\[ m_{\text{acid}} \times V_{\text{acid}} = m_{\text{base}} \times V_{\text{base}} \]

This equation allows for the calculation of the volume of the titrant needed to reach the equivalence point if it is not provided. Understanding these concepts is essential for accurately determining the pH at the equivalence point in a titration involving a weak acid and a strong base.