A 1.00 L buffer solution is 0.250 M in HF and 0.250 M in NaF. Calculate the pH of the solution after the addition of 100.0 mL of 1.00 M HCl. (Ka = 3.5 x 10^-4) (a) 4.11(b) 3.82(c) 3.46(d) 3.09

Verified step by step guidance

1. Identify the components of the buffer solution: HF (weak acid) and NaF (its conjugate base).
2. Use the Henderson-Hasselbalch equation: \( \text{pH} = \text{pKa} + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right) \), where \( \text{pKa} = -\log(\text{Ka}) \).
3. Calculate the initial moles of HF and NaF in the buffer: \( \text{moles of HF} = 0.250 \text{ M} \times 1.00 \text{ L} \) and \( \text{moles of NaF} = 0.250 \text{ M} \times 1.00 \text{ L} \).
4. Determine the moles of HCl added: \( 1.00 \text{ M} \times 0.100 \text{ L} \). HCl will react with NaF to form HF, changing the concentrations of HF and NaF.
5. Recalculate the concentrations of HF and NaF after the reaction and use the Henderson-Hasselbalch equation to find the new pH.

Key Concepts

Buffer Solutions

A buffer solution is a system that resists changes in pH upon the addition of small amounts of acid or base. It typically consists of a weak acid and its conjugate base, which in this case are HF and NaF. The weak acid can neutralize added bases, while the conjugate base can neutralize added acids, maintaining a relatively stable pH.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation relates the pH of a buffer solution to the concentration of the weak acid and its conjugate base. It is expressed as pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant (Ka). This equation is essential for calculating the pH of buffer solutions before and after the addition of acids or bases.

Acid-Base Neutralization

When an acid is added to a buffer solution, it reacts with the conjugate base present in the buffer. In this scenario, the addition of HCl will react with NaF, converting some of the NaF into HF. This reaction alters the concentrations of the components in the buffer, which must be accounted for when calculating the new pH using the Henderson-Hasselbalch equation.