Question

Write the formula of the conjugate acid or base of the following substances.

Acids

1. HCl2. HCO3–

Base

1.CN-2. H2O

Answer 1

The conjugate acid/base for the species 

$HCL_2$ , $HCO_3$ are $Cl^-$ and $CO^{3-}$

And for $CN^{-2}$ , $H_2O$ are $CN^-$ and $O^{2-}$