Calculating NaC2H3O2 Concentration for Desired pH in Acetic Acid Solutions

In acid-base chemistry, it is crucial to understand how the concentrations of salts and acids affect the pH of a solution. Specifically, the Henderson-Hasselbalch equation is a powerful tool for calculating the pH of a buffer solution, such as a solution of acetic acid and sodium acetate. This article will guide you through the process of determining the concentration of sodium acetate (NaC2H3O2) needed to achieve a specific pH in a solution of acetic acid (CH3COOH).

Introduction to the Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a fundamental concept in biochemistry and chemistry, particularly in the study of buffers. It is used to calculate the pH of a buffer solution, which is a solution that resists changes in pH when small amounts of acid or base are added to it. The equation is given by:

pH pKa log10[A-/HA]

Using the Henderson-Hasselbalch Equation to Calculate pH

Let's consider the case where we want to achieve a pH of 4.90 in a 0.10 M solution of acetic acid. Acetic acid has a known pKa value of 4.7. We will use the Henderson-Hasselbalch equation to determine the required concentration of sodium acetate (NaC2H3O2) to achieve this pH.

Step 1: Rearrange the Equation

We start by rearranging the Henderson-Hasselbalch equation to solve for the ratio of [A-] to [HA]. The equation becomes:

log10 [A-/HA] pH - pKa

[A-/HA] 10(pH - pKa)

Step 2: Plug in the Values

Now, let's plug in the given values. The desired pH is 4.90, the pKa of acetic acid is 4.7, and the concentration of acetic acid is 0.10 M. Performing the calculations step by step, we get:

4.90 - 4.7 0.20

100.20 ≈ 1.5849

The ratio of [A-] to [HA] is approximately 1.5849. This means that for every molecule of acetic acid, there should be 1.5849 molecules of sodium acetate to achieve the desired pH.

Step 3: Calculate [A-]

Now, we can calculate the concentration of sodium acetate [A-]. The concentration of acetic acid [HA] is 0.10 M. Therefore:

[A-] 1.5849 × 0.10 M

[A-] ≈ 0.15849 M

Conclusion

To achieve a pH of 4.90 in a 0.10 M solution of acetic acid, the concentration of sodium acetate must be approximately 0.158 M. This calculation demonstrates the practical application of the Henderson-Hasselbalch equation in determining the required concentrations of acid and salt to create a buffer solution of a specific pH.

Additional Practical Applications

The Henderson-Hasselbalch equation is not limited to acetic acid and sodium acetate. It can be applied to other weak acids and their respective sodium salts. This equation is particularly useful in biochemistry, where buffer solutions are used to maintain a stable pH in various biochemical reactions and cell cultures.

Keyword Optimization

This article has been optimized for search engines by using relevant keywords such as Henderson-Hasselbalch Equation, Acetic Acid, and pH Calculation. These keywords should help improve the article's visibility in Google searches related to pH calculations and buffer solutions.