What mass (in grams) of sodium acetate (CH3COONa) must be added to 100.00 mL of a 0.115 M solution of acetic acid in order to prepare a buffer solution with a pH of 4.70? The K, of acetic acid is 1.8 x 105. Mass of sodium acetate =

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### Buffer Solution Calculation

To prepare a buffer solution, it is essential to calculate the required mass of a solute. Here we are tasked with finding the mass of sodium acetate (CH₃COONa) needed to prepare a buffer solution. 

#### Problem:
What mass (in grams) of sodium acetate (CH₃COONa) must be added to 100.00 mL of a 0.115 M solution of acetic acid in order to prepare a buffer solution with a pH of 4.70? The \( \text{K}_\text{a} \) of acetic acid is \( 1.8 \times 10^{-5} \).

**Mass of sodium acetate =** \( \_\_\_\_\_\_\_\_\_ \text{g} \)

---

#### Explanation:

To solve this problem, we can use the Henderson-Hasselbalch equation, which is given by:

\[ \text{pH} = \text{p}K_\text{a} + \log{\left(\frac{[\text{A}^-]}{[\text{HA}]}\right)} \]

Where:
- \( \text{pH} \) is the desired pH of the buffer solution.
- \( \text{p}K_\text{a} \) is the negative logarithm of the acid dissociation constant (Kₐ).
- \( [\text{A}^-] \) is the concentration of the conjugate base (sodium acetate).
- \( [\text{HA}] \) is the concentration of the acid (acetic acid).

Given the values:
- Desired pH = 4.70
- \( \text{K}_\text{a} = 1.8 \times 10^{-5} \)
- Volume of the acetic acid solution = 100.00 mL
- Molarity of the acetic acid solution = 0.115 M

First, calculate the pKₐ:
\[ \text{p}K_\text{a} = -\log(1.8 \times 10^{-5}) \approx 4.74 \]

By substituting into the Henderson-Hasselbalch equation:
\[ 4.70 = 4.74 + \log{\left(\frac{[\text{A}^-]}{0.115}\right)}
Transcribed Image Text:### Buffer Solution Calculation To prepare a buffer solution, it is essential to calculate the required mass of a solute. Here we are tasked with finding the mass of sodium acetate (CH₃COONa) needed to prepare a buffer solution. #### Problem: What mass (in grams) of sodium acetate (CH₃COONa) must be added to 100.00 mL of a 0.115 M solution of acetic acid in order to prepare a buffer solution with a pH of 4.70? The \( \text{K}_\text{a} \) of acetic acid is \( 1.8 \times 10^{-5} \). **Mass of sodium acetate =** \( \_\_\_\_\_\_\_\_\_ \text{g} \) --- #### Explanation: To solve this problem, we can use the Henderson-Hasselbalch equation, which is given by: \[ \text{pH} = \text{p}K_\text{a} + \log{\left(\frac{[\text{A}^-]}{[\text{HA}]}\right)} \] Where: - \( \text{pH} \) is the desired pH of the buffer solution. - \( \text{p}K_\text{a} \) is the negative logarithm of the acid dissociation constant (Kₐ). - \( [\text{A}^-] \) is the concentration of the conjugate base (sodium acetate). - \( [\text{HA}] \) is the concentration of the acid (acetic acid). Given the values: - Desired pH = 4.70 - \( \text{K}_\text{a} = 1.8 \times 10^{-5} \) - Volume of the acetic acid solution = 100.00 mL - Molarity of the acetic acid solution = 0.115 M First, calculate the pKₐ: \[ \text{p}K_\text{a} = -\log(1.8 \times 10^{-5}) \approx 4.74 \] By substituting into the Henderson-Hasselbalch equation: \[ 4.70 = 4.74 + \log{\left(\frac{[\text{A}^-]}{0.115}\right)}
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