Calculate the pH after 0.010 mol of HCl is added to 250.0mL of a 0.050

Chemistry
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ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
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**Problem Statement:**

Calculate the pH after 0.010 mol of HCl is added to 250.0 mL of a 0.050 M NH₃/0.15 M NH₄Cl solution.

**Solution:**

The problem involves calculating the pH of a buffer solution containing ammonia (NH₃) and ammonium chloride (NH₄Cl) after the addition of hydrochloric acid (HCl).

1. **Understand the Buffer Solution:**
   - The solution contains 0.050 M NH₃ and 0.15 M NH₄Cl. 
   - NH₃ acts as a weak base, and NH₄⁺ is its conjugate acid.

2. **Reaction with HCl:**
   - When 0.010 mol of HCl is added, it reacts with NH₃.
   - The reaction: 
     \[
     \text{NH}_3 + \text{HCl} \rightarrow \text{NH}_4^+ + \text{Cl}^-
     \]
   - This increases the concentration of NH₄⁺.

3. **Use Henderson-Hasselbalch Equation:**
   - The equation for buffer solutions: 
     \[
     \text{pH} = \text{p}K_a + \log \left( \frac{[\text{base}]}{[\text{acid}]} \right)
     \]
   - Determine \([\text{base}] = [\text{NH}_3]\) and \([\text{acid}] = [\text{NH}_4^+]\).

4. **Calculate New Concentrations:**
   - Initial moles of NH₃ = 0.050 M × 0.250 L = 0.0125 mol.
   - Initial moles of NH₄Cl = 0.15 M × 0.250 L = 0.0375 mol.
   - After the reaction with HCl, moles of NH₄⁺ become 0.0475 mol (0.0375 + 0.010) and moles of NH₃ become 0.0025 mol (0.0125 - 0.010).

5. **Calculate pH:**
   - Substitute values into the Henderson-Hasselbalch equation to find the pH of the resulting solution.
Transcribed Image Text:**Problem Statement:** Calculate the pH after 0.010 mol of HCl is added to 250.0 mL of a 0.050 M NH₃/0.15 M NH₄Cl solution. **Solution:** The problem involves calculating the pH of a buffer solution containing ammonia (NH₃) and ammonium chloride (NH₄Cl) after the addition of hydrochloric acid (HCl). 1. **Understand the Buffer Solution:** - The solution contains 0.050 M NH₃ and 0.15 M NH₄Cl. - NH₃ acts as a weak base, and NH₄⁺ is its conjugate acid. 2. **Reaction with HCl:** - When 0.010 mol of HCl is added, it reacts with NH₃. - The reaction: \[ \text{NH}_3 + \text{HCl} \rightarrow \text{NH}_4^+ + \text{Cl}^- \] - This increases the concentration of NH₄⁺. 3. **Use Henderson-Hasselbalch Equation:** - The equation for buffer solutions: \[ \text{pH} = \text{p}K_a + \log \left( \frac{[\text{base}]}{[\text{acid}]} \right) \] - Determine \([\text{base}] = [\text{NH}_3]\) and \([\text{acid}] = [\text{NH}_4^+]\). 4. **Calculate New Concentrations:** - Initial moles of NH₃ = 0.050 M × 0.250 L = 0.0125 mol. - Initial moles of NH₄Cl = 0.15 M × 0.250 L = 0.0375 mol. - After the reaction with HCl, moles of NH₄⁺ become 0.0475 mol (0.0375 + 0.010) and moles of NH₃ become 0.0025 mol (0.0125 - 0.010). 5. **Calculate pH:** - Substitute values into the Henderson-Hasselbalch equation to find the pH of the resulting solution.
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