The isomolecular pairs are those that have identical molecular shapes due to similar electron domain geometries. In this set:
- \(\mathrm{XeO}_3\) and \(\mathrm{H}_3\mathrm{O}^+\) both have trigonal pyramidal shapes.
- \(\mathrm{SO}_3\) and \(\mathrm{CO}_3^{2-}\) both have trigonal planar shapes.
At STP \(x\) g of a metal hydrogen carbonate (MHCO$_3$) (molar mass \(84 \, {g/mol}\)) on heating gives CO$_2$, which can completely react with \(0.02 \, {moles}\) of MOH (molar mass \(40 \, {g/mol}\)) to give MHCO$_3$. The value of \(x\) is: