Ion–dipole forces Original Scenario-Based Download PDF

Questions

1. 1.

   A deep-space extraction probe collects crystalline salts from an icy moon and dissolves them into liquid hydrogen cyanide (HCN), a highly polar molecular solvent. The automated spectrometer measures the strength of the ion–dipole forces stabilizing the dissolved metal cations in solution. When comparing magnesium ions ($\text{Mg}^{2+}$) and sodium ions ($\text{Na}^{+}$), which possess nearly identical ionic radii, the sensors record significantly stronger solvation forces for magnesium. Which statement correctly accounts for the difference in ion–dipole attraction strength between these two ions and the solvent molecules?

   • A) Sodium ions generate stronger ion–dipole interactions because their single charge minimizes steric repulsion between adjacent solvent molecules in the primary coordination shell.
   • B) Magnesium ions generate stronger ion–dipole interactions because their higher ionic charge produces a greater charge density, exerting a stronger electrostatic force on the polar solvent molecules.
   • C) Sodium ions generate stronger ion–dipole interactions because lower-charge cations establish coordinate covalent bonds rather than purely electrostatic dipoles with solvent molecules.
   • D) Magnesium ions generate weaker ion–dipole interactions because multivalent charges destabilize the solvent coordination sphere through mutual dipole cancellation.