# Mg is not precipitated in group V because

(a) $MgCO_3$ is soluble in water
(b) $MgCO_3$ is soluble in $NH_4Cl$
(c) $MgCO_3$ is soluble in $NH_4OH$
(d) None of these

The concentration of $CO^{2-}$ ions is very low which does not prevent the ionic product of $Mg^{2+}$ and $CO^{2-}_3$ ions to surpass the solubility product in the presence of $NH_4Cl$.