Question

A 75.0-mL volume of 0.200 mol L^−1 NH3 (Kb=1.8×10^−5) is titrated with 0.500 mol L^−1 HNO3. Calculate the pH after the addition of 19.0 mL of HNO3.

Answer 1

To calculate the pH after the addition of 19.0 mL of HNO3 in a titration involving NH3 and HNO3, determine the moles of HNO3 added, the moles of NH3 remaining, and the concentration of OH-. Use the concentration of OH- to find the pH using the expression pH = 14 - pOH.

To calculate the pH after the addition of 19.0 mL of HNO3 in a titration involving NH3 and HNO3, we need to determine the moles of HNO3 added and the moles of NH3 remaining.

Then, we can use the equilibrium equation for NH3 to calculate the concentration of OH-. Finally, we can use the concentration of OH- to find the pH using the expression pH = 14 - pOH.

Step 1: Calculate the moles of HNO3 added. Moles of HNO3 = Volume of HNO3 added (in L) × Molarity of HNO3.

Step 2: Calculate the moles of NH3 remaining. Moles of NH3 remaining = Initial moles of NH3 - Moles of HNO3 added.

Step 3: Calculate the concentration of OH-. Concentration of OH- = Moles of NH3 remaining / Total volume (in L).

Step 4: Calculate the pH. pH = 14 - pOH = 14 + log([OH-]).