When temporary hard water containing $\mathrm{Mg}{\left({\mathrm{HCO}}_3\right)}_2$ is boiled, the ppt. formed is of

$\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$ is less soluble than ${\mathrm{MgCO}}_3$. On boiling temporary hard water containing ${\mathrm{Mg}}^{+2}$ ions, the ppt. obtained is of $\mathrm{Mg}{\left(\mathrm{OH}\right)}_2$ are not that of ${\mathrm{MgCO}}_3$.