What is the pH of a 1.0 L buffer made with 0.300 mol of HF (Ka = 6.8 × 10-4) and 0.200 mol of NaF to which 0.070 mol of HCI were added? %3D

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### Buffer pH Calculation Example

#### Problem Statement:
What is the pH of a 1.0 L buffer made with 0.300 mol of HF (Ka = 6.8 × 10⁻⁴) and 0.200 mol of NaF to which 0.070 mol of HCl were added?

#### Explanation:

We can calculate the pH of the buffer solution using the Henderson-Hasselbalch equation:
\[ \text{pH} = \text{p}K_a + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right) \]

Where:
- \(\text{p}K_a\) is the negative logarithm of the acid dissociation constant (\(K_a\)).
- \([\text{A}^-]\) is the concentration of the conjugate base (F⁻ from NaF).
- \([\text{HA}]\) is the concentration of the weak acid (HF).

**Steps to solve the problem:**

1. **Calculate \(\text{p}K_a\):**
\[ \text{p}K_a = -\log(6.8 \times 10^{-4}) \]

2. **Determine the changes in molarity due to the addition of HCl:**

   - Upon adding 0.070 mol of HCl to the buffer, HCl will react completely with the conjugate base NaF.
   - \( 0.070 \text{ mol} \) HCl will reduce the amount of \( \text{A}^- (F^-) \) and increase the amount of \(\text{HA (HF)}\).

   Initial moles before the reaction:
   - HF: 0.300 mol
   - NaF: 0.200 mol

   Change in moles after addition of HCl:
   - HF: 0.300 mol + 0.070 mol = 0.370 mol
   - NaF: 0.200 mol - 0.070 mol = 0.130 mol

3. **Apply the Henderson-Hasselbalch equation:**

\[ \text{pH} = \text{p}K_a + \log \left( \frac{0.130}{0.370} \right) \]
   
#### Diagram Explanation:
The image contains a
Transcribed Image Text:### Buffer pH Calculation Example #### Problem Statement: What is the pH of a 1.0 L buffer made with 0.300 mol of HF (Ka = 6.8 × 10⁻⁴) and 0.200 mol of NaF to which 0.070 mol of HCl were added? #### Explanation: We can calculate the pH of the buffer solution using the Henderson-Hasselbalch equation: \[ \text{pH} = \text{p}K_a + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right) \] Where: - \(\text{p}K_a\) is the negative logarithm of the acid dissociation constant (\(K_a\)). - \([\text{A}^-]\) is the concentration of the conjugate base (F⁻ from NaF). - \([\text{HA}]\) is the concentration of the weak acid (HF). **Steps to solve the problem:** 1. **Calculate \(\text{p}K_a\):** \[ \text{p}K_a = -\log(6.8 \times 10^{-4}) \] 2. **Determine the changes in molarity due to the addition of HCl:** - Upon adding 0.070 mol of HCl to the buffer, HCl will react completely with the conjugate base NaF. - \( 0.070 \text{ mol} \) HCl will reduce the amount of \( \text{A}^- (F^-) \) and increase the amount of \(\text{HA (HF)}\). Initial moles before the reaction: - HF: 0.300 mol - NaF: 0.200 mol Change in moles after addition of HCl: - HF: 0.300 mol + 0.070 mol = 0.370 mol - NaF: 0.200 mol - 0.070 mol = 0.130 mol 3. **Apply the Henderson-Hasselbalch equation:** \[ \text{pH} = \text{p}K_a + \log \left( \frac{0.130}{0.370} \right) \] #### Diagram Explanation: The image contains a
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