Metallurgy

Let's analyze each option in terms of whether it contains water of crystallization or is associated with water molecules:Cryolite ( $\mathrm{Na}_3\mathrm{AlF}_6$ )→ This compound does not contain water molecules. It is anhydrous (no water of crystallization).✓ Not associated with water molecules.Bauxite $(\mathrm{Al}_2\mathrm{O}_3 \cdot \times \mathrm{H}_2\mathrm{O})$→ This is a hydrated form of alumina, i.e. it does contain water molecules.- Associated with water.Kernite $(\mathrm{Na}_2\mathrm{B}_4\mathrm{O}_7 \cdot 4 \mathrm{H}_2\mathrm{O})$→ This is hydrated sodium borate, contains crystallization water.- Associated with water.Borax $(\mathrm{Na}_{2}\mathrm{B}_{4}\mathrm{O}_{7} \cdot 10 \mathrm{H}_{2}\mathrm{O}$ )→ This also contains crystal water.- Associated with water.Correct Answer: Option A - CryoliteReason: Cryolite $(\mathrm{Na}_3\mathrm{AlF}_6)$ is not associated with water molecules.