Which is the best acid-base pair to use in the preparation of a buffer with pH = 10.5? (a) HOI and OI- (Ka = 2.0 x 10^-11) (b) HNO2 and NO2- (Ka = 4.5 x 10^-4) (c) HIO3 and IO3- (Ka = 1.7 x 10^-1) (d) H2PO4^- and HPO4^2- (Ka = 6.2 x 10^-8)

Name: Chemistry
Author: McMurry
ISBN: 9781292336145

검증된 단계별 안내

Step 1: Understand that a buffer solution is most effective when the pH is close to the pKa of the acid in the acid-base pair.

Step 2: Calculate the pKa for each acid using the formula pKa = -log(Ka).

Step 3: Compare the calculated pKa values to the desired pH of 10.5.

Step 4: Identify the acid-base pair whose pKa is closest to the desired pH of 10.5.

Step 5: Select the acid-base pair with the pKa closest to 10.5 as the best choice for the buffer solution.

주요 개념

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

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. The effectiveness of a buffer is determined by the pKa of the acid and the desired pH, which should be close to the pKa for optimal buffering capacity.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation relates the pH of a buffer solution to the pKa of the acid and the ratio of the concentrations of the conjugate base to the weak acid. It is expressed as pH = pKa + log([A-]/[HA]). This equation is crucial for determining the appropriate acid-base pair to achieve a specific pH, such as 10.5 in this case.

Acid Dissociation Constant (Ka)

The acid dissociation constant (Ka) quantifies the strength of an acid in solution, indicating how well it donates protons (H+) to the solution. A higher Ka value corresponds to a stronger acid, which is more effective at maintaining the desired pH in a buffer. When selecting an acid-base pair for a buffer, the pKa (the negative logarithm of Ka) should be close to the target pH for optimal performance.