Question

Identify a species which is 'NOT' a Bronsted acid but a Lewis acid

• A. $B{F}_3$
• B. $H_3^{+}O$
• C. $N{H}_3$
• D. HCl

Answer 1

Answer: (A)

Bronsted defined an acid as a substance, which has a tendency to give a proton $\left(H^{+}\right)$, on the other hand Lewis proposed an acid as a substance, which is capable of accepting a pair of electrons. As $H_3{O}^{+}$, $N{H}_3$ and HCl has $H^{+}$ ions, these are Bronsted acids whereas $B{F}_3$ is an electron deficiet molecule, thus be have like a Lewis acid, i.e., electron pair acceptor.