Explanation
(a) The balanced equation of the reaction is:
[tex]2Al_{(s)}+6HCl_{(g)}\rightarrow2AlCl_{3(s)}+3H_2[/tex]
The compound F is solid AlCl₃
(b) When the solid AlCl₃ is heated to 900 °C, it changes from a solid to a gaseous state. The illustration of the change is shown below:
[tex]\text{AlCl}_{3(s)}+heat(900^oC)\rightarrow AlCl_{(g)}[/tex]
(c) Melting point of AlF₃ is high as compared to AlCl₃ because AlF₃ is an ionic compound while AlCl₃ is a covalent compound but the bond in AlCl₃ is a polar covalent bond. Melting points of ionic compounds are usually high as compared to covalent bonds because an ionic bond is stronger as compared to covalent bonds. Also, AlCl₃ has a simple molecular structure with weak van der Waals forces between its molecules. More energy is needed to overcome the strong ionic bonds in AlF₃ than the weak intermolecular forces in AlCl₃, hence AlF₃ has a much higher melting point.
