Calculate Ph of 0.11m Solution of Ch3coona Solution

This calculator helps you determine the pH of a 0.11 molar solution of sodium acetate (CH3COONa). Sodium acetate is a weak base that forms an acetate buffer solution when dissolved in water. The pH of this solution can be calculated using the Henderson-Hasselbalch equation.

Introduction

Sodium acetate (CH3COONa) is a salt formed by the reaction between acetic acid (CH3COOH) and sodium hydroxide (NaOH). When dissolved in water, it dissociates into acetate ions (CH3COO⁻) and sodium ions (Na⁺). The acetate ions can react with water to form acetic acid and hydroxide ions, creating a buffer solution.

The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation, which relates the pH to the ratio of the concentrations of the conjugate base to the conjugate acid. For a solution of sodium acetate, the equation is:

Henderson-Hasselbalch Equation:

pH = pKa + log₁₀([CH3COO⁻]/[CH3COOH])

Where:

pKa is the acid dissociation constant of acetic acid (4.76 at 25°C)
[CH3COO⁻] is the concentration of acetate ions
[CH3COOH] is the concentration of acetic acid

How to Calculate

To calculate the pH of a 0.11M solution of sodium acetate:

Determine the concentration of acetate ions ([CH3COO⁻]). For a 0.11M solution of sodium acetate, [CH3COO⁻] = 0.11M.
Determine the concentration of acetic acid ([CH3COOH]). Since sodium acetate is a salt, it does not contribute to the concentration of acetic acid. Therefore, [CH3COOH] = 0.
Use the Henderson-Hasselbalch equation to calculate the pH.

Note: When [CH3COOH] = 0, the Henderson-Hasselbalch equation simplifies to pH = pKa + log₁₀([CH3COO⁻]/0). Since division by zero is undefined, we must consider the limiting behavior of the equation as [CH3COOH] approaches zero.

Example Calculation

Let's calculate the pH of a 0.11M solution of sodium acetate:

Given:

pKa of acetic acid = 4.76

[CH3COO⁻] = 0.11M

[CH3COOH] = 0M

Calculation:

Since [CH3COOH] = 0, we can consider the limiting behavior of the Henderson-Hasselbalch equation. As [CH3COOH] approaches zero, the term log₁₀([CH3COO⁻]/[CH3COOH]) approaches infinity. Therefore, the pH approaches infinity, indicating a strongly basic solution.

Result:

The pH of a 0.11M solution of sodium acetate is approximately 14, indicating a strongly basic solution.

Interpretation

A pH of 14 for a 0.11M solution of sodium acetate indicates that the solution is strongly basic. This is expected because sodium acetate is a salt of a weak acid (acetic acid) and a strong base (sodium hydroxide). The acetate ions (CH3COO⁻) react with water to form hydroxide ions (OH⁻), increasing the concentration of hydroxide ions and lowering the concentration of hydrogen ions (H⁺).

This solution can be used as a buffer to maintain a constant pH in chemical reactions or as a base in various industrial and laboratory applications.

FAQ

What is the pKa of acetic acid?

The pKa of acetic acid is 4.76 at 25°C. This value represents the acid dissociation constant of acetic acid, which is the equilibrium constant for the reaction of acetic acid with water to form acetate ions and hydrogen ions.

Why is the pH of a 0.11M sodium acetate solution so high?

The pH of a 0.11M sodium acetate solution is high because sodium acetate is a salt of a weak acid (acetic acid) and a strong base (sodium hydroxide). The acetate ions (CH3COO⁻) react with water to form hydroxide ions (OH⁻), increasing the concentration of hydroxide ions and lowering the concentration of hydrogen ions (H⁺).

Can sodium acetate be used as a buffer solution?

Yes, sodium acetate can be used as a buffer solution. The acetate ions (CH3COO⁻) and acetic acid (CH3COOH) can react with added acid or base to maintain a relatively constant pH.