Final answer:
Lattice energy significantly influences the physical properties of ionic compounds. They typically have high melting and boiling points, are hard but brittle, exist as solids at room temperature, and conduct electricity when dissolved in water.
Step-by-step explanation:
Lattice energy is a fundamental characteristic of ionic compounds, which have strong electrostatic attractions between oppositely charged ions. The questions pertain to the physical properties that are influenced by this energy. Here's a detailed explanation:
- (a) Have high melting and boiling points. Ionic compounds indeed have high melting and boiling points. The strong electrostatic forces of attraction in an ionic lattice mean that considerable energy is required to break these bonds and change the state of the compound from solid to liquid or gas.
- (b) Are hard. The rigid and robust crystal lattice structure makes ionic compounds hard. However, they are also brittle and can shatter when subjected to stress.
- Most ionic compounds exist solely as solids at room temperature due to their high lattice energies, which results in high melting points.
- (d) Are good conductors of electricity when dissolved in water. While ionic compounds do not conduct electricity in their solid state due to the immobilization of ions, they do conduct electricity when dissolved in water as the ions are free to move and carry charge.
All these properties are attributable to the significant lattice energy present in ionic compounds, reflecting the strength of the ionic bonds and the stability of the ionic lattice structure.