35.0mL of 0.050 M HCl is titrated with 0.050 M NH3 (Kb= 1.8 x 10^-5). The pH of the analyte solution after 15.0mL addition of NH3 titrant is?

Answer 1

NH3 + HCl ==> NH4Cl

mols NH3 = M x L = ?
mols HCl = M x L = ?
Subtract mols HCl - mols NH3. I think HCl is in excess but you should confirm that. .
That means pH = =log (HCl).