A 20.0-mL sample of 0.200 M HBr solution is titrated with 0.200 M NaOH solution. Calculate the pH of the solution after the following volumes of base have been added: (e) 35.0 mL.

검증된 단계별 안내

Calculate the initial moles of HBr in the solution using the formula: \( \text{moles} = \text{concentration} \times \text{volume} \).

Calculate the moles of NaOH added using the same formula: \( \text{moles} = \text{concentration} \times \text{volume} \).

Determine the limiting reactant by comparing the moles of HBr and NaOH. Since both are strong acid and base, they will react in a 1:1 ratio.

Calculate the moles of excess NaOH after the reaction, if any, by subtracting the moles of HBr from the moles of NaOH.

Calculate the pH of the solution. If NaOH is in excess, use the concentration of excess OH\(^-\) ions to find the pOH, and then use \( \text{pH} = 14 - \text{pOH} \). If HBr is in excess, use the concentration of excess H\(^+\) ions to find the pH directly.

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주요 개념

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Acid-Base Neutralization

In a titration involving a strong acid like HBr and a strong base like NaOH, the acid and base react in a neutralization reaction to form water and a salt. The stoichiometry of the reaction is 1:1, meaning one mole of HBr reacts with one mole of NaOH. Understanding this concept is crucial for determining the amount of acid and base present at any point during the titration.

pH Calculation

pH is a measure of the hydrogen ion concentration in a solution, calculated using the formula pH = -log[H+]. In a titration, the pH changes as the acid is neutralized by the base. After the equivalence point, the solution will contain excess hydroxide ions, and the pH can be calculated based on the concentration of these ions.

Equivalence Point

The equivalence point in a titration is reached when the amount of titrant added is stoichiometrically equivalent to the amount of substance being titrated. For the given reaction, this occurs when the moles of NaOH added equal the moles of HBr initially present. Beyond this point, the solution will be basic, and understanding its location is essential for calculating the resulting pH.