An 8.36 g sample of NH4Cl was added to 26.0 mL of 1.00 M NaOH and the resulting solution diluted to 0.100 L. What is the pH of this buffer solution?

• A. 5.75
• B. 7.00
• C. 11.00
• D. 9.25

Answer: (D)

Verified step by step guidance

1. Calculate the moles of NH4Cl using its molar mass. The molar mass of NH4Cl is approximately 53.49 g/mol. Use the formula: moles = mass / molar mass.
2. Calculate the moles of NaOH using its concentration and volume. Use the formula: moles = concentration (M) × volume (L). Convert the volume from mL to L before using it in the calculation.
3. Determine the limiting reactant between NH4Cl and NaOH. The reaction between NH4Cl and NaOH produces NH3 and H2O. Compare the moles of NH4Cl and NaOH to find which one is the limiting reactant.
4. Calculate the concentration of NH3 in the final solution. Subtract the moles of the limiting reactant from the other reactant to find the moles of NH3 formed. Then, divide by the total volume of the solution (0.100 L) to find the concentration.
5. Use the Henderson-Hasselbalch equation to find the pH of the buffer solution. The equation is: pH = pKa + log([base]/[acid]). Use the concentration of NH3 as the base and the concentration of NH4+ (from NH4Cl) as the acid. The pKa of NH4+ is approximately 9.25.