- Ionic compounds are defined by high melting points, brittle crystalline lattices, and electrical conductivity in molten or aqueous states.
- Compound W has a low melting point and molecular structure, indicating covalent character.
- Compound X lacks conductivity in water, making it an unlikely candidate for a typical ionic compound.
- Compound Z features a very high melting point (\(801^\circ \text{C}\)) and brittleness, which are definitive traits of ionic bonding.
- The most likely ionic compound is \(\boxed{\text{Z}}\).
Explanation
- Analysis of Properties of Ionic Compounds
To identify the ionic compound, we analyze the characteristics of each provided compound against the standard physical and chemical properties of ionic compounds. Ionic compounds typically form crystalline structures that are brittle at room temperature and have very high melting points due to the strong electrostatic forces (ionic bonds) holding the lattice together. They are also characterized by their ability to conduct electricity when melted or dissolved in water, as these processes liberate the ions so they can act as charge carriers.
- Evaluation of the Compounds
Evaluating each compound based on the observations provided:
- Compound W: This is a hard solid with a low melting point (\(44^\circ \text{C}\)) and a molecular structure. Low melting points and molecular structures are hallmark characteristics of covalent compounds, not ionic ones.
- Compound X: This is a brittle solid with a crystal structure, but it does not conduct electricity in water. While brittleness and crystal structure are common in ionic compounds, the lack of electrical conductivity in water is highly uncharacteristic for most ionic substances, which readily dissociate into ions in aqueous solutions.
- Compound Y: This is a hard solid that conducts electricity and has a molecular structure. Conduction is not typical for molecular structures, and this description is more consistent with a metallic or a specific network covalent structure.
- Compound Z: This is a brittle solid with a very high melting point (\(801^\circ \text{C}\)). The combination of high melting point, brittleness, and crystal structure is the classic signature of an ionic crystal lattice (for instance, sodium chloride, NaCl, shares these exact properties).
- Conclusion
Comparing all candidates, Compound Z exhibits the most consistent physical and chemical properties associated with ionic compounds—specifically the high melting point and the brittle, crystalline nature. Therefore, Z is the most likely candidate. The final answer is \(\boxed{\text{Z}}\).
Examples
In real-life chemistry laboratories, identifying unknown substances often begins by measuring physical properties like melting points and conductivity. For example, if a chemist finds a white, brittle, crystalline powder that does not melt when held in their hand but conducts electricity when dissolved in water, they can confidently classify it as an ionic salt rather than a volatile organic molecule. These tests serve as a foundation for understanding the strength of chemical bonds.