Substance X and substance Y have nearly identical molar masses. Molecules of X can hydrogen-bond with each other, whereas molecules of Y interact only through London dispersion forces. Which statement correctly predicts how the phase-transition temperatures of X compare with those of Y at 1 atm?
a) X has a lower melting point but a higher boiling point than Y because hydrogen bonding mainly affects vaporization.
b) X has both a higher melting point and a higher boiling point than Y because stronger intermolecular forces in X require more energy for both transitions.
c) X and Y have similar melting points but X has a higher boiling point because dispersion forces dominate in the solid state.
d) X and Y have nearly identical melting and boiling points because intermolecular forces depend primarily on molar mass.