CHEMISTRY · Single correct · A Level · Chemistry · Bonding · Bonding
Problem
Three ionic solids—MgO, NaCl, and CsI—are each placed in liquid ammonia (a moderately polar solvent with weaker hydrogen-bonding ability than water) at 25∘C. Which solid is most likely to have the lowest molar solubility in this solvent?
(a) CsI, because its large ions form the weakest ion–dipole interactions with ammonia.
(b) MgO, because its highly charged ions create a large lattice enthalpy that the solvent cannot offset with ion–dipole interactions.
(c) NaCl, because its lattice enthalpy is greater than that of MgO, making dissolution least favorable.
(d) MgO, because dissolution would greatly decrease the entropy of the system.