Properties of ionic compounds Transitional Reasoning Practice

Questions

1. 1.

   In a laboratory investigation of an unidentified solid substance, a student records three primary observations: • The substance possesses a high melting point well above 750 °C. • Dry crystals of the substance do not conduct electricity, but dissolving them in distilled water produces an electrically conductive solution. • Striking a crystal with a firm mechanical impact causes it to shatter cleanly along smooth planes rather than flatten or bend. Which deduction correctly relates these macroscopic observations to the submicroscopic structure of the substance?

   • A) Its high melting point arises from weak intermolecular forces between neutral molecules, and electrical conductivity in water is driven by the movement of delocalized electrons.
   • B) Its brittleness results from layers of neutral atoms sliding smoothly across an electron sea, which prevents permanent disruption of bonding upon impact.
   • C) Its lack of solid-state conductivity occurs because free valence electrons are permanently localized into covalent bonds that release neutral molecules into solution.
   • D) Its brittleness occurs because mechanical stress forces ions of identical charge to align and repel each other, while its electrical conductivity in water is enabled by freely mobile ions.

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