OK, resolve this paradox. The triple point is said to be unique because all 3 phases of a pure compound are in equilibrium at that pressure and temperature. And that equilibrium extends over an enormous pressure range and a modest temperature range as well. So the triple point has the vapor too at the external pressure. The ocean is about 0.60 M NaCl.
Oxygen exerts a powerful electron-withdrawing effect on the species to which it's bonded.
So in both compounds, the hydrogens on a carbon to which the oxygen is bonded lose some of their electron density and become partially positive. That makes them attractive to the oxygens from neighboring molecules. So ethanal's aldehyde hydrogen is more attractive to a neighbor's oxygen, and the intermolecular force is expected to be stronger. Look at the geometry of those molecules. O H making a pair harder to separate.