Aluminium trichloride (AlCl3) sublimes at a relatively low temperature of 180°C due to its molecular structure and the nature of its bonds. Let's analyze the given options:
The intermolecular forces between Al2Cl6 molecules are weak: This is a valid point. Sublimation occurs when the intermolecular forces are weak enough to allow the substance to transition directly from a solid to a gas phase without passing through the liquid phase.
The coordinate bonds between aluminum and chlorine are weak: Coordinate bonds, also known as dative covalent bonds, occur when both electrons in the bond come from one atom. In the case of AlCl3, each chlorine atom contributes one electron pair to form coordinate bonds with the aluminum atom. If these bonds were weak, it would contribute to the substance's ability to sublime. So, this statement is valid.
The covalent bonds between aluminum and chlorine are weak: This statement seems inaccurate. While covalent bonds are present between aluminum and chlorine atoms in AlCl3, these bonds are typically strong. Weak covalent bonds wouldn't necessarily lead to sublimation at a low temperature.
So, based on the analysis:
Option A: All statements are not entirely correct.
Option B: The first two statements are correct and align with the reasons for AlCl3's sublimation. This seems to be the most appropriate choice.
Option C: The second statement is correct, but the third statement seems incorrect.
Option D: Only the first statement is correct, but it alone doesn't fully explain the low sublimation temperature of AlCl3.
Therefore, the most appropriate answer seems to be B. 1 and 2 only are correct.
