Question

The conjugate base of $ {{H}_{3}}B{{O}_{3}} $ is.

Answer 1

Hint: We know that According to Bronsted Lowry acid base theory, acid is a proton donor and base is a proton acceptor. When an acid loses a proton, a conjugate base is obtained. When a base accepts a proton, a conjugate acid is obtained.

Complete answer:
Firstly we should be aware that the question is regarding the combining capacity of any atom of any element with another element. We can say that a conjugate base is what we can describe as a leftover after an acid has donated a proton during a chemical reaction. Hence we get that a conjugate base is a derivative species that is formed by the removal of a proton from an acid. This can be considered as in the reverse reaction it is able to gain a hydrogen ion. Because some acids are capable of releasing multiple protons, we can say that the conjugate base of an acid could in turn itself be acidic. Apart from that a more general definition is that a conjugate base is the base member of a pair of compounds that transform into each other by gaining or losing a proton.
Although we are taught that the conjugate base of an acid is what you get after removing a proton. But here $ {{H}_{3}}B{{O}_{3}} $ doesn't give out a proton so easily. This is because of the formation of an unstable anion. Rather it accepts a lone pair of electrons from Lewis bases like $ N{{H}_{3}},\text{ }O{{H}^{-}} $ etc.
So the conjugate base of this acid depends on which reaction its participation in. $ {{H}_{3}}B{{O}_{3}}+O{{H}^{{}}}-\to \text{ }{{\left[ B{{\left( OH \right)}_{4}} \right]}^{-}} $
So here $ {{\left[ B\left( O{{H}_{4}} \right) \right]}^{-}} $ serves as the conjugate base of $ {{H}_{3}}B{{O}_{3}}. $

Note:
Remember that the Bronsted Lowry acid base theory is similar to Arrhenius' concept of acid and base. The Arrhenius concept is limited to aqueous solutions. However, Bronsted Lowry theory can also be applied to non-aqueous solutions. In Arrhenius theory, a base gives a hydroxide ion. In Bronsted Lowry theory, a base accepts a proton.