Considering the Arrhenius theory of acids and bases:

  1. Is every existing compound either an acid or a base?
  2. Why is a compound such as $ \ce {NH_3}$ considered a base, if it doesn't even have an oxygen atom and a base is supposed to release $ \ce {OH-}$ in water?
  3. If $X$ is a base according to Arrhenius theory, will $X$ still be a base according to the other two theories (and the same if $X$ were an acid)?

According to the Brønsted-Lowry theory:

  1. There are no absolute acid and bases, but only acid-base reaction in which one compound acts as a base and the other as an acid. So, is every reaction of two compounds an acid-base one?
  2. Except for water, are there any other substances which in some reactions act as bases while in others as acids?

closed as too broad by Mithoron, M.A.R. ಠ_ಠ, airhuff, Melanie Shebel, Todd Minehardt Jul 30 '17 at 17:52

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    $\begingroup$ Ammonia is the very reason chemists had to rethink the Arrhenius theory. $\endgroup$ – M.A.R. ಠ_ಠ Feb 11 '15 at 21:01

A couple of thoughts:

There are mainly 3 different definitions of acids and bases:

  1. The Arrhenius formulation: Acid = proton donor in water, Based = hydroxide ion donor in water
  2. The Brønsted-Lowry formulation: Acid = potential proton donor, Base = potential proton acceptor
  3. The Lewis formulation: Acid = Electron pair acceptor, Base = Electron pair donor

The Lewis definition is the most general, followed by the BL and finally by the Arrhenius definition.

You are right, for example HCl is considered a strong acid in water, but it is very weakly acidic in glacial acetic acid. If you follow the Lewis definition a large number of reactions will be considered acid base reactions. An exception are free-radical based reactions

There are many compounds that are amphoteric, but it really also depends on the definition you use.


Not the answer you're looking for? Browse other questions tagged or ask your own question.