What is the pH of a buffer solution prepared by mixing 200 mL of 0.05 M aqueous ammonia with 100 mL of 0.01 M ammonium chloride? [Given: pK_b of NH₃ = 4.74 ]

Step-by-step solution

Millimoles of NH₃ = 200 0.05 = 10 Millimoles of NH₄Cl = 100 0.01 = 1 Total volume = 300 mL [NH₃] = 10 300 M [NH₄^+] = 1 300 M Using the Henderson-Hasselbalch equation for a basic buffer: pOH = pK_b + ( [NH₄^+] [NH₃] ) pOH = 4.74 + ( 1/300 10/300 ) pOH = 4.74 + (10⁻¹) = 4.74 - 1 = 3.74 pH = 14 - pOH = 14 - 3.74 = 10.26 Answer: 10.26