Give the conjugate acid and conjugate base of the following:
$(i)$ $(CH_3)_2NH$
$(ii)$ $HPO_4^{2-}$
$(iii)$ $HS^{-}$

(N/A) The conjugate acid is formed by adding $H^+$ and the conjugate base is formed by removing $H^+$.
$(i)$ For $(CH_3)_2NH$: Conjugate acid is $(CH_3)_2NH_2^+$ and conjugate base is $(CH_3)_2N^-$.
$(ii)$ For $HPO_4^{2-}$: Conjugate acid is $H_2PO_4^-$ and conjugate base is $PO_4^{3-}$.
$(iii)$ For $HS^-$: Conjugate acid is $H_2S$ and conjugate base is $S^{2-}$.