Julie S. answered • 03/31/17
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I was skimming through the questions and ran across this one - this is not a neutral salt "because it is formed from a weak acid and a weak base". It is the conjugate acid of a weak base (NH4+ is the conjugate acid of NH3) and the conjugate base of a weak acid (NO2- is the conjugate base of HNO2).
So yes, it is a weak acid (NH4+) and weak base (NO2-).
But you have to compare the Ka and Kb for these species before making a judgement! The Ka for NH4+ can be found by Kw/(Kb for NH3) and the Kb for NO2- can be found by Kw/(Ka for HNO2).
Ka for NH4+ is 1.00 x 10^-14 / 1.8 x 10^-5 = 5.6 x 10^-10
Kb for NO2- is 1.00 x 10^-14 / 4.5 x 10^-4 = 2.2 x 10^-11
Therefore the acid strength here is slightly higher than the base strength. The solution should be slightly acidic.
