Given the following $K_a$ values,determine which species is the strongest base: $HSO_4^- = 1.2 \times 10^{-2}$,$H_2PO_4^- = 6.3 \times 10^{-8}$,$HCO_3^- = 4.7 \times 10^{-11}$.

Identify the conjugate base of ${H_2}PO_3^-$ and the conjugate acid of ${HCO_3^-}$.

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 $NH_{3(aq)}$

The conjugate base of $H_2PO_4^-$ is

Select the set of amphiprotic species.

Explain the Arrhenius concept of acids and bases.