Calculate the pH at the equivalence point in titrating 0.100 M solutions of each of the following with 0.080 M NaOH: (a) hydrobromic acid (HBr).

Verified step by step guidance

1. Identify the type of acid involved in the titration. Hydrobromic acid (HBr) is a strong acid.
2. Recognize that at the equivalence point, the moles of acid equal the moles of base added. Since HBr is a strong acid, it will completely dissociate in water.
3. Write the balanced chemical equation for the reaction: \[ \text{HBr} + \text{NaOH} \rightarrow \text{NaBr} + \text{H}_2\text{O} \]
4. At the equivalence point, the solution contains the salt NaBr. Since NaBr is formed from a strong acid and a strong base, it does not affect the pH of the solution.
5. Conclude that the pH at the equivalence point for the titration of a strong acid with a strong base is neutral, which is a pH of 7.

Key Concepts

Titration and Equivalence Point

Titration is a quantitative analytical method used to determine the concentration of a solute in a solution. The equivalence point occurs when the amount of titrant added is stoichiometrically equivalent to the amount of analyte in the solution, resulting in complete neutralization. At this point, the pH of the solution is determined by the properties of the resulting solution, which can vary depending on the strength of the acid and base involved.

Strong Acid vs. Strong Base

Hydrobromic acid (HBr) is a strong acid that completely dissociates in solution, while sodium hydroxide (NaOH) is a strong base that also fully dissociates. In a titration involving a strong acid and a strong base, the pH at the equivalence point is typically neutral (pH 7) because the resulting solution contains only water and the salt formed from the acid and base, which does not affect the pH significantly.

pH Calculation

The pH is a measure of the hydrogen ion concentration in a solution, calculated using the formula pH = -log[H+]. At the equivalence point of a strong acid-strong base titration, the pH can be calculated based on the concentrations of the reactants and the volume of titrant added. Since both HBr and NaOH are strong, the resulting solution at the equivalence point will have a pH close to 7, indicating neutrality.