What is the Lewis acid in the following reaction? NH3 + BI3 → I3BNH3

NH3

BI3

I3BNH3

none of these

The correct answer is BI₃

Lewis acid refers to a compound that could accept a pair of electrons, while Lewis base refers to a compound that could donate a pair of electrons.

In the mentioned reaction,

In NH₃, nitrogen exhibits a lone pair of electrons and is functioning as a Lewis base. In BI₃, the boron is deficient for an electron pair, thus in order to complete its octet it functions as a Lewis acid.