Question

Classify each of the following solids as metallic, network covalent, ionic, or molecular. (a) It is insoluble in water, melts above \(500^{\circ} \mathrm{C},\) and does not conduct electricity either as a solid, dissolved in water, or molten. (b) It dissolves in water but does not conduct electricity as an aqueous solution, as a solid, or when molten. (c) It dissolves in water, melts above \(100^{\circ} \mathrm{C},\) and conducts electricity when present in an aqueous solution.

Short answer

Question: Based on the properties provided, classify each solid as metallic, network covalent, ionic, or molecular. (a) Insoluble in water, high melting point, does not conduct electricity in any state. (b) Dissolves in water, does not conduct electricity in any state. (c) Dissolves in water, melting point above 100°C, conducts electricity when present in an aqueous solution. Answer: (a) network covalent (b) molecular (c) ionic

Step-by-step solution

(a) Classification of the solid based on its properties

The given solid is insoluble in water, has a high melting point, and does not conduct electricity in any state. These properties suggest that the solid has a network covalent structure. Network covalent solids are typically formed from atoms that are connected by a continuous network of covalent bonds, which results in their high melting points and poor electrical conductivities.

(b) Classification of the solid based on its properties

The given solid dissolves in water but does not conduct electricity in any state. Based on these properties, we can classify this solid as a molecular solid. Molecular solids typically consist of molecules held together by weak intermolecular forces, such as van der Waals forces or hydrogen bonds. The fact that this solid dissolves in water suggests the presence of polar molecules with possible hydrogen bonding, but its inability to conduct electricity shows that it doesn't contain mobile charge carriers.

(c) Classification of the solid based on its properties

The given solid dissolves in water, has a melting point above 100°C, and conducts electricity when present in an aqueous solution. These properties indicate that the solid has an ionic structure. Ionic solids are composed of positively and negatively charged ions held together by strong electrostatic forces (ionic bonds). The high melting point of this solid is due to the strong ionic bonds that require a large amount of energy to break. Additionally, ionic solids usually dissolve in water and conduct electricity when dissolved or molten, as their ions become mobile charge carriers.