Apentix/AP Chemistry/Unit 2: Molecular and Ionic Compound Structure and Properties/Question
AP Chemistryhardmcq1 pt

Which comparison of lattice energies is correct?

A.NaCl has the larger magnitude, because its ions sit farther apart
B.Both have equal magnitudes because both crystals contain equal numbers of ions
C.MgO has the larger magnitude, because its 2+ and 2- charges multiply the Coulombic attraction
D.Neither comparison can be made without measuring both solids

Explanation

Core Concept

Lattice energy scales with the product of ionic charges and inversely with interionic distance. MgO pairs a 2+ cation with a 2- anion, quadrupling the attraction relative to the 1-times-1 pairing in NaCl. Smaller Mg²⁺ and O²⁻ radii shorten the distance further, pushing MgO's magnitude far beyond NaCl's.

Correct Answer

CMgO has the larger magnitude, because its 2+ and 2- charges multiply the Coulombic attraction

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