Follow the directions of Question 64. Consider two beakers:...

Follow the directions of Question 64. Consider two beakers: Beaker A has a weak acid $\left(K_{\mathrm{a}}=1 \times 10^{-5}\right)$ Beaker B has HCl. The volume and molarity of each acid in the beakers are the same. Both acids are to be titrated with a $0.1 \mathrm{M}$ solution of $\mathrm{NaOH}$ (a) Before titration starts (at zero time), the pH of the solution in Beaker $A$ is _________ the $p H$ of the solution in Beaker B. (b) At half-neutralization (halfway to the equivalence point), the $\mathrm{pH}$ of the solution in Beaker $\mathrm{A}$ __________ the $\mathrm{pH}$ of the solution in Beaker $\mathrm{B}$. (c) When each solution has reached its equivalence point, the $\mathrm{pH}$ of the solution in Beaker $\mathrm{A} $ _________ the $\mathrm{pH}$ of the solution in Beaker B. (d) At the equivalence point, the volume of $\mathrm{NaOH}$ used to titrate HCl in Beaker B ________ the volume of $\mathrm{NaOH}$ used to titrate the weak acid in Beaker A.

Follow the directions of Question 64. Consider two beakers:
Beaker A has a weak acid $\left(K_{\mathrm{a}}=1 \times 10^{-5}\right)$ Beaker B has HCl.
The volume and molarity of each acid in the beakers are the same. Both acids are to be titrated with a $0.1 \mathrm{M}$ solution of $\mathrm{NaOH}$
(a) Before titration starts (at zero time), the pH of the solution in Beaker $A$ is _________ the $p H$ of the solution in Beaker B.
(b) At half-neutralization (halfway to the equivalence point), the $\mathrm{pH}$ of the solution in Beaker $\mathrm{A}$ __________ the $\mathrm{pH}$ of the solution in Beaker $\mathrm{B}$.
(c) When each solution has reached its equivalence point, the $\mathrm{pH}$ of the solution in Beaker $\mathrm{A} $ _________ the $\mathrm{pH}$ of the solution in Beaker B.
(d) At the equivalence point, the volume of $\mathrm{NaOH}$ used to titrate HCl in Beaker B ________ the volume of $\mathrm{NaOH}$ used to titrate the weak acid in Beaker A.

Key Concepts

Titration Stoichiometry and Volume Relationships

The volume of titrant required to reach the equivalence point is determined by the stoichiometric relationship between the acid and base. When the molarity and initial volume of the acid are the same, the equivalence point is reached after adding an equal number of moles of titrant, regardless of the acid strength, although the pH at equivalence may vary due to the acid’s properties.

Buffer Systems and the Henderson-Hasselbalch Equation

At the half-equivalence point of titration for a weak acid, the solution forms a buffer consisting of equal concentrations of the weak acid and its conjugate base. The Henderson-Hasselbalch equation is used to calculate the pH of this buffer, and at this specific point the pH equals the pKa of the weak acid.

Equivalence Point and Salt Hydrolysis

The equivalence point is reached when the moles of titrant added exactly neutralize the moles of the acid. In titrating a weak acid, the resulting salt can hydrolyze in water, leading to a basic solution, whereas titrating a strong acid typically produces a neutral solution at equivalence.

Acid-Base Titration

Acid-base titration is an analytical method used to determine the concentration of an acid or base by gradually adding a titrant of known concentration until the reaction reaches its equivalence point. The process involves monitoring changes in pH and understanding the reaction stoichiometry between the titrant and the analyte.

Weak Acid versus Strong Acid

A weak acid only partially dissociates in solution, resulting in a higher pH compared to a strong acid, which completely dissociates. In titration, this difference in dissociation behavior influences the initial pH of the solution as well as the shape of the titration curve, making the weak acid system act as a buffer over a range of pH.

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