Question

Acidity of $B{F}_3$ can be explained on the basis of which of the following concepts?

• A. Arrhenius concept
• B. Lewis concept
• C. Bronsted Lowry as well as Lewis concept
• D. Bronsted Lowry concept

Answer 1

The correct option is B Lewis concept

$\text{Arrhenius concept}:$

According to it, an acid releases $\left[H^{+}\right]$ in aqueous solution while base release $\left[O{H}^{-}\right]$ ion in aqueous solution.

e.g.;
Acid:

$HCl\left(aq\right)\to H^{+}\left(aq\right)+C{l}^{-}\left(aq\right)$

Base:

$NaOH\left(aq\right)\to N{a}^{+}\left(aq\right)+O{H}^{-}\left(aq\right)$

$\text{Bronsted Lowry concept}:$

An acid is a substance that donate $H^{+}$ ion while a base is a substance that accepts $H^{+}$ ion.
e.g.;

$N{H}_3+HCl\to {N{H}_4}^{+}C{l}^{-}$

$Base,Accepting{H}^{+}$ $Acid,donating{H}^{+}$

$\text{Lewis’s concept}:$

An acid is a species which accepts lone pair of $e^{-}$ in a reaction while a base donates that lone pair of $e^{-}$

e.g.;

$N{H}_3+H^{+}\to {N{H}_4}^{+}$

(Lewis's base) (Lewis acid)

Since $B{F}_3$ does not have $H$ atom, it does not fit into the definition of Arrhenius concept.

$B{F}_3$ can’t be Lowry bronsted acid as it cannot donate $H^{+}$ ion and not a Lowry Bronsted base because it cannot accept $H^{+}$ ion since it does not have a lone pair on the central atom Boron.

$B{F}_3$ is an electron deficient species as it can accept a lone pair of electrons from electron rich species.

Thus, it fits into the definition of Lewis acid. Thus, $B{F}_3$ is Lewis’s acid and it can be explained on the basis of Lewis theory of acid and base.

The correct option is $\left(C\right)$ i.e., Lewis’s concept.