Predicting Structures (Edexcel A Level Chemistry)

• Different types of structure and bonding have different effects on the physical properties of substances such as their melting and boiling points, electrical conductivity and solubility

Characteristics of Different Compound Structure Types Table

Answer

The correct answer is Statement 4

• • The relatively high melting point, solubility in water and electrical conductivity when molten suggest that X is a giant ionic structure.
  • The low melting point of Y suggests that little energy is needed to break the lattice which corresponds to a simple molecular structure. This is further supported by the low electrical conductivity and its being almost insoluble in water.
  • Compound Z has a very high melting point which is characteristic of either metallic or giant molecular lattices, however since it conducts electricity, compound Z must be a giant metallic lattice.

Answer:

The correct option is A

• • A high melting point is characteristic of a giant structure, which could be metallic, ionic or covalent
  • The poor conductivity as a liquid and solid would match a giant covalent or network covalent structure