Asked in ETEA MDCAT 2008 2008Moderate

The etectrical conductivity of NaCl crystal is:

Correct answer: D. NaCl crystal doesn't conduct electric current

  • A. More than NaBr crystal
  • B. Less than NaBr crystal
  • C. Equal to NaBr crystal
  • D. NaCl crystal doesn't conduct electric current

Explanation

In solid form, NaCl does not conduct electricity because its ions are locked in place within the crystal lattice and cannot move freely. For a substance to conduct electricity, it must have free-moving charged particles, which solid NaCl lacks. However, when NaCl is molten or dissolved in water, the ions are free to move, allowing it to conduct electricity. NaBr behaves similarly, with neither conducting in solid form, but both conducting when molten or in solution. Therefore, options A, B, and C are incorrect because they assume electrical conduction in solid form.

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About Ionic and Molecular Crystals

Ionic crystals contain oppositely charged ions held by electrostatic forces, whereas molecular crystals contain discrete molecules joined by weaker intermolecular forces. Their structures explain differences in melting point, hardness, volatility, solubility and electrical conductivity, especially between solid and molten states.

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