What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH₃ with 5.00 mL of 0.10 M NH₄Cl? Assume that the volume of the solutions are additive and that K_b = 1.8 × 10^-5for NH₃. A)8)25 B)10.26 C)10.25 D)11.13

Question

Quizplus · Accepted Answer

Step 1: Calculate the moles of NaH2PO4 and Na2HPO4 using the formula:
moles = concentration × volume (in liters)
moles NaH2PO4 = 0.10 mol/L × 50.00 mL / 1000 mL/L = 0.0050 mol
moles Na2HPO4 = 0.10 mol/L × 5.00 mL / 1000 mL/L = 0.00050 mol

Step 2: Calculate the total moles of H+ and OH- ions using the formula:
moles H+ = moles Na2HPO4
moles OH- = moles NaOH + moles NaH2PO4 - moles HCl
moles NaOH = 0.10 mol/L × 25.00 mL / 1000 mL/L = 0.0025 mol
moles HCl = 0.10 mol/L × 2.50 mL / 1000 mL/L = 0.00025 mol
moles OH- = 0.0025 mol + 0.0050 mol - 0.00025 mol = 0.00725 mol

Step 3: Calculate the concentration of H+ ions using the formula:
[H+] = Kw / [OH-]
Kw = 1.0 × 10^-14 mol^2/L^2 (at 25°C)
[H+] = 1.0 × 10^-14 mol^2/L^2 / 0.00725 mol/L = 1.38 × 10^-12 mol/L
pH = -log[H+] = -log(1.38 × 10^-12) = 10.25

What Is the PH of a Solution Prepared by Mixing