Question

Why is ammonia not an arrhenius base?

Answer 1

Well, Arrhenius bases are conceived to be sources of the hydroxide ion in aqueous solution...

Explanation:

And since ammonia does NOT contain hydroxide ions, i.e. its chemical formula is `NH_3`, it does not fall under the Arrhenius' umbrella. We classify ammonia as a Bronsted-Lowry base...and its conjugate acid is ammonium ion, `NH_4^+`...

`NH_3(aq) + H_2O(l) rightleftharpoonsNH_4^+ + HO^-`

`K_b=1.80xx10^-5`

Note that this is all conceived to occur in AQUEOUS solution, i.e. in a water solvent. In liquid ammonia solvent, and use of this solvent is nowadays fairly standard and straightforward....the following acid-base regime obtains...

`2NH_3(l)rightleftharpoonsunderbrace(NH_2^(-))_"the amide ion" + NH_4^+`

Ammonia has a normal boiling point of `33.3` `""^@C`...
The degree of dissociation can be measured, but I don't my text at hand right now....