mmoles of NH3 = 60.0 x 0.100 = 6.00
Kb = 1.8 x 10^-5
pKb = 4.74 , pKa = 9.26
a)
mmoles of HCl = 40.5 x 0.150 = 6.075
NH3 +  HCl  Â
------------>Â Â NH4+Cl-
6.00Â Â Â Â Â Â
6.075Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
0
0Â Â Â Â Â Â Â Â Â Â
0.075Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
6.00
here strong acid remains. so
concentration of H+ = 0.075 / 60 + 40.5
                             Â
= 7.46 x 10^-4 M
pH = - log (7.46 x 10^-4)
pH = 3.13
b)
mmoles of HCl = 60 x 0.150 = 9
NH3 +  HCl  Â
------------>Â Â NH4+Cl-
6.00Â Â Â Â Â Â 9.00
                      Â
0
0Â Â Â Â Â Â Â Â Â 3.00
                    Â
6.00
here strong acid remains. so
[H+] = 3 / 120 = 0.025 M
pH = 1.60
