Acid Base Theories

hms.tech

what theories out of the major two ( Bronsted-Lowry Theory of acids and bases and The Lewis Theory of acids and bases) should we use in common problems, and which one is more reliable ?

Borek

Brønsted-Lowry. Lewis theory doesn't give a way to make quantitative predictions.

Acut

Borek, despite agreeing with your answer, I'm puzzled with its justification. In which cases would Bronsted-Lowry give a quantitative prediction (and Lewis' theory would fail to do so)?

I always thought that Arrhenius, Bronsted-Lowry and Lewis were all entirely qualitative definitions - simply defining what an acid and a base were and giving an idea of which reactions where possible.

Borek

It is not possible to use Lewis theory to create unambiguous acidity scale. Acid strength can be only determined relative to the selected base (and vice versa), and quite often it happens that depending on the selected base results are opposite (what seems to be a stronger base becomes a weak base after selecting different base as a reference point). In the case of Brønsted-Lowry this is not a problem, even if you move to different solvent relative strengths of acids are identical (or at least their ordering doesn't change - what was stronger is still stronger). In a way that's because proton gives a reference point, but proton presence (or autodissociation of a protic solvent) is one of the theory assumptions.

Try to find Adam Hulanicki's book Reactions of acids and bases in analytical chemistry for some more details (I guess it is n ot a problem to find discussion in other sources, this one I have here so I know it addresses the problem).

Acut

As always, Borek makes me learn something new!

Sadly, I couldn't find the book you suggested on my college's libraries. Do you have any other suggestions for books on the subject?

Borek

Sorry, no. I don't have an easy access to the library so I have to work with what I have at home.