Calculate the pH of each of the following buffered solutions. a. 0.50 M C2H5NHH2 / 0.25 M

step 1 Okay, there are a total of three parts in the given question. For part A over here, the concentr

Calculate the pH of each of the following buffered...

Calculate the pH of each of the following buffered solutions. $$ \begin{array}{l}{\text { a. } 0.50 M \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NHH}_{2} / 0.25 M \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{Cl}} \\ {\text { b. } 0.25 M \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} / 0.50 M \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{Cl}} \\ {\text { c. } 0.50 \mathrm{M} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} / 0.50 \mathrm{M} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{Cl}}\end{array} $$

Calculate the pH of each of the following buffered solutions.
$$
\begin{array}{l}{\text { a. } 0.50 M \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NHH}_{2} / 0.25 M \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{Cl}} \\ {\text { b. } 0.25 M \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} / 0.50 M \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{Cl}} \\ {\text { c. } 0.50 \mathrm{M} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} / 0.50 \mathrm{M} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{3} \mathrm{Cl}}\end{array}
$$

Key Concepts

Buffer Solution

A buffer solution is designed to resist 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, allowing it to maintain a relatively constant pH in the face of perturbations. The functional balance between the weak acid and conjugate base components is central to a buffer’s ability to maintain a stable pH.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to estimate the pH of a buffer solution. It relates the pH to the pKa of the weak acid and the logarithm of the ratio of the concentrations of the conjugate base to the weak acid. This equation is particularly useful because it simplifies pH calculations for buffer systems by directly linking the chemical makeup to the pH outcome.

Conjugate Acid-Base Pair

A conjugate acid-base pair consists of two species that transform into each other by the gain or loss of a proton. In a buffer system, the weak base reacts with water to produce its conjugate acid, or a weak acid loses a proton to form its conjugate base. Understanding these pairs is crucial in analyzing buffer behavior, as the equilibrium between the conjugate forms is responsible for the system’s resistance to pH changes.

Acid-Base Equilibria and pKa/pKb Relationship

Acid-base equilibria describe the balance between the dissociated and undissociated forms of acids and bases in solution. For weak acids and bases, the strength is quantified by their acid dissociation constant (Ka) and base dissociation constant (Kb), respectively. The pKa (and pKb) values are logarithmic measures of these constants. In buffer calculations, converting between pKb of a weak base and the pKa of its conjugate acid (using the relationship pKa + pKb = 14 in aqueous solutions) is essential for correctly applying the Henderson-Hasselbalch equation.

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