Calculate the pH of buffers that contain the acid and...

Calculate the pH of buffers that contain the acid and conjugate base concentrations listed below. a. $\left[\mathrm{CH}_3 \mathrm{COOH}\right]=0.40 \mathrm{M},\left[\mathrm{CH}_3 \mathrm{COO}^{-}\right]=0.25 \mathrm{M}$ b. $\left[\mathrm{H}_2 \mathrm{PO}_4^{-}\right]=0.10 \mathrm{M},\left[\mathrm{HPO}_4{ }^{2-}\right]=0.40 \mathrm{M}$ c. $\left[\mathrm{HSO}_3{ }^{-}\right]=1.50 \mathrm{M},\left[\mathrm{SO}_3{ }^{2-}\right]=0.20 \mathrm{M}$

Calculate the pH of buffers that contain the acid and conjugate base concentrations listed below.
a. $\left[\mathrm{CH}_3 \mathrm{COOH}\right]=0.40 \mathrm{M},\left[\mathrm{CH}_3 \mathrm{COO}^{-}\right]=0.25 \mathrm{M}$
b. $\left[\mathrm{H}_2 \mathrm{PO}_4^{-}\right]=0.10 \mathrm{M},\left[\mathrm{HPO}_4{ }^{2-}\right]=0.40 \mathrm{M}$
c. $\left[\mathrm{HSO}_3{ }^{-}\right]=1.50 \mathrm{M},\left[\mathrm{SO}_3{ }^{2-}\right]=0.20 \mathrm{M}$

Key Concepts

Buffer Solutions

A buffer solution is a system that resists significant changes in pH when small amounts of an acid or a base are added. It typically consists of a weak acid and its conjugate base, or a weak base and its conjugate acid. Understanding how buffers work is essential for controlling pH in many chemical, biological, and industrial processes.

Conjugate Acid-Base Pairs

Conjugate acid-base pairs are two chemical species that differ by one proton. In a buffer, the weak acid donates a proton to form its conjugate base, and the conjugate base can accept a proton to re-form the acid. This reversible reaction is what enables the buffer to maintain a relatively constant pH.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical expression that relates the pH of a buffer solution to the pKa (acid dissociation constant) of the weak acid and the ratio of the concentrations of the conjugate base to the acid. This equation is widely used to calculate the pH of buffer solutions and to design buffers with specific pH values.

Acid Dissociation Constant (pKa)

The pKa value is the negative logarithm of the acid dissociation constant (Ka) of a weak acid. It provides a measure of the strength of the acid, with lower pKa values indicating stronger acids. In the context of buffers, the pKa is an important parameter in determining the pH and the effective buffering range of the acid-conjugate base system.

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