Question

Explain why:
(i) $BCl_{3}$ is a Lewis acid.
(ii) Boric acid is a monobasic acid.

Answer 1

i) A compound "accepts" a electrons pair from donor called Lewis acid.

Due to electron deficient nature of $B{ Cl }_{ 3 }$, it accepts a electrons from "electron rich" species compound like ammonia.

The central atom of boron trichloride is boron as it is an electron deficient and it accepts a "electrons pairs" and act as Lewis acid.

ii) "Boric acid" is often referred to as orthoboric acid. Although, Boric acid contains three OH groups, it can still act as a monobasic acid instead of a tri-basic acid. "Boric acid" does not act as a protons donor, but rather accepts a "lone pair" of electrons from "OH ions". Therefore, it can be act as monobasic Lewis acid.