A 25.0-mL sample of 0.125 M pyridine is titrated with 0.100 M HCl. Calculate the pH at each volume of added acid: 40 mL.

검증된 단계별 안내

Identify the reaction: Pyridine (C5H5N) is a weak base and reacts with HCl, a strong acid, to form pyridinium ion (C5H5NH+).

Calculate the initial moles of pyridine using its concentration and volume: \( \text{moles of pyridine} = 0.125 \text{ M} \times 0.025 \text{ L} \).

Calculate the moles of HCl added using its concentration and volume: \( \text{moles of HCl} = 0.100 \text{ M} \times 0.040 \text{ L} \).

Determine the limiting reactant and calculate the moles of pyridinium ion formed and any excess reactant remaining after the reaction.

Use the Henderson-Hasselbalch equation to calculate the pH: \( \text{pH} = \text{pK}_a + \log \left( \frac{[\text{base}]}{[\text{acid}]} \right) \), where \( \text{pK}_a \) is derived from the \( K_b \) of pyridine.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Acid-Base Titration

An acid-base titration is a quantitative analytical method used to determine the concentration of an acid or base in a solution. In this process, a solution of known concentration (the titrant) is added to a solution of unknown concentration until the reaction reaches its equivalence point, where the amount of acid equals the amount of base. The pH changes during the titration, and monitoring these changes allows for the calculation of the unknown concentration.

Buffer Solutions

A buffer solution is a system that resists changes in pH upon the addition of small amounts of acid or base. It typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid. In the context of the titration of pyridine (a weak base) with HCl (a strong acid), the buffer capacity is crucial for understanding how the pH will change before and after the equivalence point.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a buffer solution. It relates the pH of the solution to the pKa of the weak acid and the ratio of the concentrations of the conjugate base and the weak acid. This equation is particularly useful in titration problems, as it allows for the determination of pH at various points during the titration, especially when the solution is still in the buffer region.