Question

What are the limitations of Bronsted lowry theory?

Answer 1

According to Bronsted lowry's theory, an acid is which can donate a proton and form a conjugate base and a base is the one which can accept a proton and form a conjugate acid.

The limitations of Bronsted lowry theory are shown below.

1. This theory could not explain the acid-base behaviour in aprotic solvents like Benzene(${\mathrm{C}}_6{\mathrm{H}}_6$), etc.
2. Since there is no proton transfer reaction between acid oxides, for example, Sulphur dioxide and Carbon dioxide respectively and basic oxides for example Calcium oxide $\left(\mathrm{CaO}\right)$and Magnesium oxide $\left(\mathrm{MgO}\right)$ respectively. It failed to explain this type of reaction.
3. It failed to exhibit the acidic nature of substances like Aluminium chloride(${\mathrm{AlCl}}_3$) and Boron trifluoride(${\mathrm{BF}}_3$) with no proton.
4. Example of Bronsted lowry acid is shown below.
   $$\begin{gathered} {\mathrm{NH}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\rightleftharpoons {{\mathrm{NH}}_4}^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right) \\ \mathrm{base}\mathrm{acid}\mathrm{Conjugate}\mathrm{acid}\mathrm{Conjugate}\mathrm{base} \end{gathered}$$
5. Here, water(${\mathrm{H}}_2\mathrm{O}$) is acting as Bronsted lowry acid and Ammonia(${\mathrm{NH}}_3$) is acting as Bronsted lowry's base.