\(H _2 \ddot{ O :} \longrightarrow \text { Lewis base }\)
\(BF _3 \longrightarrow \text { Lewis acid }\)
\(\ddot{ :O :}H \longrightarrow \text { Lewis base }\)
\(\ddot{ N } H _3 \longrightarrow \text { Lewis base }\)
($BaCO_3$ માટે $K_{sp}$ =$ 5 .1 \times 10^{-9}$)