The reactions involved are as follows:
(I)
HCl+NH3(aq)→NH4Cl (II) CH3COOH+NH3(aq)→CH3COONH4
(III)
H2SO4+2NH3(aq)→(NH4)2SO4 Now, according to Henderson Haselbach equation
pH=pKa+log() =14−pKb+log() =9.26+log() Thus, pH depends on the strength of conjugate acid. The order acid strength of the reactants is as follows:
CH3COOH<HCl<H2SO4..Also
NH3(aq) is a strong base. As conjugate base of weak acid is strongly acidic, we have the acidic strength of products as
CH3COONH4>NH4Cl<(NH4)2SO4
That is, (II) > (I) > (III).