Answer :
The pH of the resulting buffer solution is 6.92. Option C is the correct answer.
To calculate the pH of the resulting buffer solution, we can use the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
Given:
- Volume of NaOH solution = 500.0 mL = 0.5 L
- Concentration of NaOH = 0.160 M
- Volume of weak acid solution = 595 mL = 0.595 L
- Concentration of weak acid = 0.250 M
- Ka of the weak acid = 1.69 × 10^-5 M
1. Calculate the moles of NaOH and weak acid:
Moles of NaOH = 0.160 M × 0.5 L = 0.080 mol
Moles of weak acid = 0.250 M × 0.595 L = 0.1488 mol
2. Determine the limiting reactant and the resulting concentrations:
The NaOH is the limiting reactant.
Concentration of conjugate base (A-) = 0.080 mol / 1.095 L = 0.073 M
Concentration of weak acid (HA) = (0.1488 mol - 0.080 mol) / 1.095 L = 0.063 M
3. Calculate the pH using the Henderson-Hasselbalch equation:
pKa = -log(1.69 × 10^-5) = 4.77
pH = 4.77 + log(0.073 / 0.063)
pH = 6.92
Therefore, the pH of the resulting buffer solution is 6.92.
The correct answer is option C.
