The pH of the solution after the addition of 18.0 mL of KOH is 1.27.
In this titration, a 50.0-mL volume of 0.15 M HBr is titrated with 0.25 M KOH. To calculate the pH after the addition of 18.0 mL of KOH, we need to determine the number of moles of HBr that have reacted with KOH.
Step 1: Calculate the moles of KOH used: (0.25 M) * (0.0180 L) = 0.00450 mol KOH
Step 2: Calculate the moles of HBr reacted: 0.00450 mol KOH * (1 mol HBr / 1 mol KOH) = 0.00450 mol HBr
Step 3: Calculate the new concentration of HBr in the solution: 0.00450 mol HBr / (0.0500 L + 0.0180 L) = 0.0535 M HBr
Step 4: Calculate the pH using the formula: pH = -log[H+]
pH = -log(0.0535 M) = 1.27