The base ionization constant of ethylamine (C2H5NH2) in aqueous solution is Kb = 6.41×10-4 at 25°C. Calculate the pH for the titration of 40.00 mL of a 0.1000 M solution of ethylamine with 0.1000 M HCl at the following volumes of added
HCl: 0, 5.00, 20.00, 39.90, 40.00, 40.10, and 50.00 mL.