# Calculate pH of Buffer CH_3COOH & CH_3COONa

• n77ler
In summary, the problem involves a buffer solution with a known concentration of acetic acid and acetate, and a given Ka value. The goal is to calculate the expected pH after diluting the buffer solution with deionized water. The Henderson-Hasselbalch equation can be used to solve this problem, starting with calculating the concentrations of the acid and conjugate base.
n77ler

## Homework Statement

Buffer solution : CH_3COOH (55 mL) + CH_3COONa (45 mL)
Ka (CH_3COOH) = 1.76 x 10^-5

Calculate the expected pH of your buffer solution after it has been dilted by making 10 mL of buffer up to 100 mL with deionized water.

Ice charts
n= c x v
c= n/v

## The Attempt at a Solution

I've calculated the pH for other additions of strong acids and strong bases but I'm not sure how to start this one. Little bit confused... Just the first step would be a great help :)

You haven't given enough information to start. You need to know something about the concentrations of acetic acid (55 mL?) and acetate (45 mL?).

Sorry, they are both 0.10 M

Review the Henderson-Hasselbach equation. Hint: pKa = -log[Ka]

n77ler said:

## Homework Statement

Buffer solution : CH_3COOH (55 mL) + CH_3COONa (45 mL)
Ka (CH_3COOH) = 1.76 x 10^-5

Calculate the expected pH of your buffer solution after it has been dilted by making 10 mL of buffer up to 100 mL with deionized water.

Ice charts
n= c x v
c= n/v

## The Attempt at a Solution

I've calculated the pH for other additions of strong acids and strong bases but I'm not sure how to start this one. Little bit confused... Just the first step would be a great help :)
the question is a little confusing due to the given volumes.i need help how to attempt the question.

As chemisttree already wrote: use Henderson-Hasselbalch equation. Start calculating concentrations of both acid and conjugate base. At this stage it will be simple dilution problem.

(in fact you can solve the problem without calculating these concentrations, but I guess explaining the shorter route will only confuse you more)

## 1. What is a buffer?

A buffer is a solution that resists changes in pH when small amounts of acid or base are added. It consists of a weak acid and its conjugate base, or a weak base and its conjugate acid.

## 2. How do I calculate the pH of a buffer solution?

The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([conjugate base]/[weak acid]). The pKa is the negative logarithm of the acid dissociation constant, and the concentrations of the conjugate base and weak acid can be determined from the buffer solution's composition.

## 3. What is the purpose of CH3COOH and CH3COONa in a buffer solution?

CH3COOH is a weak acid and CH3COONa is its conjugate base. Together, they make up the buffer solution and help maintain a constant pH when small amounts of acid or base are added.

## 4. What is the significance of the ratio of CH3COOH to CH3COONa in a buffer solution?

The ratio of CH3COOH to CH3COONa determines the buffering capacity of the solution. A higher ratio means a greater buffering capacity, as there is more of the weak acid to neutralize added base, or more of the conjugate base to neutralize added acid.

## 5. How does temperature affect the pH of a buffer solution?

The pH of a buffer solution may change slightly with temperature, as the dissociation of the weak acid or base may be affected. However, this effect is usually minimal and can be compensated for by adjusting the ratio of weak acid to conjugate base in the buffer solution.

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