B. The entropy increases when a solid or liquid is dissolved
in water (below). This can be illustrated by liquid methanol and
crystalline ammonium chloride.
The entropy of ammonium chloride in solution is the sum of the
entropies of the hydrated ions; this is based on a convention that
assigns an entropy of zero to the hydrated H+ ion.
Notice that the entropy changes that result from dissolving suggest
that ammonium chloride solution is much more disordered than crystalline
NH4Cl, whereas the difference in disorder between liquid
methanol and methanol in aqueous solution is small.
This is explained by the break-up of a regular array of NH4+
and Cl- ions in the crystal lattice when NH4Cl
dissolves, whereas liquid methanol has no such regular structure.