PCl5 and PbCl4 are thermally unstable. — p Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: Sublimation occurs in molecular solids that have relatively weak intermolecular forces in the solid state. Step 2: Anhydrous aluminum chloride has a dimeric structure, Al2Cl6, where individual dimers are held together only by weak van der Waals forces. Step 3: Because of these weak intermolecular forces, heating anhydrous AlCl3 causes it to sublime directly from the solid to the gas phase at around 180°C, matching option (d).