6 Solution Base NH3 Kb 2 x 105 48 4x 10434 Ionization consta

6. Solution Base NH3 Kb 2 x 105 4.8 4x 1043.4 Ionization constants of two bases are listed in the table above. A 20. mL sample of a 0.10 M solution of each base is titrated to the equivalence point with 20. mL of 0.10 M HC1. Which of the following is a true statement about the pH of the solutions at the equivalence point? (A) Solution 1 has a higher pH at the equivalence point because NH3 is the stronger base. (B) Solution 1 has a higher pH at the equivalence point because NHs has the stronger conjugate acid. (C) Solution 1 has a lower pH at the equivalence point because NH3 is the stronger base. (D) Solution 1 has a lower pH at the equivalence point because NHs has the stronger conjugate acid.

Solution

•From the values given, it can be understood that NH3 is less basic than CH3NH2.

•Hence conjugate acid of NH3 is more acidic than that of CH3NH2.

•Hence at equivalent point during reaction with hcl the pH in case of solution 1 is low as conjugate acid of NH3 is more acidic.