0.1 M solution of each of NH3 and NH4Cl are added to prepare a buffer of 1 litre solution. If 0.01 mole of HCl is added (assuming no volume change). The concentrations of NH3 and NH4Cl are
0.09, 0.11
Initial pOH
pOH = pKb + log[NH4Cl][NH3] = pKb + log0.10.1 = pKb
Number of equivalents of NH3 = N×Vlit=0.1×1 = 0.1 eq
Number of equivalents of NH4Cl = N×Vlit=0.1×1 = 0.1 eq
Number of equivalents of HCl added = 0.01 eq
NH3+HCl→NH4Cl
Initially [NH3] = 0.1, [HCl] = 0.01, [NH4Cl] = 0.1
Finally [NH3] = 0.1 – 0.01 = 0.09, [HCl] = 0, [NH4Cl] = 0.1 + 0.01 = 0.11