Question

Ammonia, NH3, if often labeled as NH4OH and called ammonium hydroxide by chemical handling companies. Many argue that this is not correct and misleading. Explain the reasoning behind calling this NH4OH. Give chemical equations to back up your explanation.

Answer 1

According to the first theory of acid and bases, Arrhenius stated that all bases delivered hydroxide ions to the solution. This worked for such substances as NaOH and KOH, but not for NH₃.

NH₃ solutions were known to be basic but there was no hydroxide in NH₃. This theory could not explain why the NH₃ acts as base without having OH within it's structure. So, to explain this Arrhenius' answer was that NH₄⁺OH^- was the actual substance, and he wrote the following equation:

NH₄OH ---> NH₄⁺ + OH^-

He did not have a concept of the solvent (water) participating in the reaction. He though the water was passive.

Years later, Bronsted-Lowry explains with their theory that and Acid is a substance capable to donate protons (H) and a base can accept the proton. So the actual reaction is:

NH₃ + H₂O ---> NH₄⁺ + OH^-

This is what it actually happens, and that's why Ammonia is NH₃ and not NH₄OH.

Hope this helps