(a) Calculate the pH of a buffer that is 0.12 M in lactic acid and 0.11 M in sodium lactate. (b)

step 1 This question wants us to calculate the pH of a buffer that has 0 .12 molar lactic acid and 0 .1

(a) Calculate the pH of a buffer that is 0.12 M in lactic...

(a) Calculate the pH of a buffer that is 0.12 $\mathrm{M}$ in lactic acid and 0.11 $\mathrm{M}$ in sodium lactate. (b) Calculate the pH of a buffer formed by mixing 85 mL of 0.13 M lactic acid with 95
mL of 0.15$M$ sodium lactate.

Key Concepts

Concentration and Dilution Effects

When solutions are mixed, the total volume and the moles of solute combine, which can change the molarity of each component. Calculations involving the mixing of solutions require accounting for the total volume to determine the final concentrations, although the ratio of the components (and therefore the pH in a buffer) might remain similar if both components are diluted proportionally.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a derivation of the acid dissociation constant expression that relates the pH of a buffer solution to the pKa (the negative logarithm of the acid dissociation constant) and the ratio of the concentrations of the conjugate base to the weak acid. This equation is particularly useful for calculating pH in buffer systems.

Buffer Solutions

Buffer solutions are mixtures that resist changes in pH when small amounts of an acid or a base are added. They usually consist of a weak acid and its conjugate base (or a weak base and its conjugate acid), which work together to neutralize added acids or bases, thereby stabilizing the pH of the solution.

Acid-Base Equilibrium

Acid-base equilibrium refers to the balance established in an aqueous solution between an acid and its conjugate base. This equilibrium is governed by the acid dissociation constant (Ka), and understanding it is essential for predicting and calculating the pH of weak acid or base solutions, including buffers.

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