Which is the strongest of the following acids?

Classify the following species into Lewis acids and Lewis bases and show how these act as Lewis acid/base:
$(a) OH^{-}$
$(b) F^{-}$
$(c) H^{+}$
$(d) BCl_{3}$

Which of the following cannot act as a Lewis or Bronsted acid?

Which two sets of reactants best represent the amphoteric character of $Zn(OH)_2$?
Set $1$ : $Zn(OH)_{2(s)}$ and $OH^{-}_{(aq)}$
Set $2$ : $Zn(OH)_{2(s)}$ and $H_2O_{(l)}$
Set $3$ : $Zn(OH)_{2(s)}$ and $H^{+}_{(aq)}$
Set $4$ : $Zn(OH)_{2(s)}$ and $NH_{3(aq)}$

Which of the following is not a Lewis acid?

Given:
$(i) \ HCN_{(aq)} + H_2O_{(l)} \rightleftharpoons H_3O^{+}_{(aq)} + CN^{-}_{(aq)}$
$K_a = 6.2 \times 10^{-10}$
$(ii) \ CN^{-}_{(aq)} + H_2O_{(l)} \rightleftharpoons HCN_{(aq)} + OH^{-}_{(aq)}$
$K_b = 1.6 \times 10^{-5}$
These equilibria show the following order of the relative base strength: