which would you think would be a stronger interaction and why: an interaction between a sodium ion and the prtial negative charge on the oxygen in ethanol, or the interaction between two ethanol molecules

The interaction between sodium ion and the partial negative charge on the oxygen is stronger.

Explanation:

The predominant interaction that exists between sodium ion and the partial negative charge on the oxygen is ion-dipole interaction.

The predominant interaction that exists between two ethanol molecules is hydrogen bonding interaction.

The order of strength of the intermolecular interactions in decreasing order:

Ionic bond > ion-dipole interaction > hydrogen bonding > dipole-dipole interaction > ion-induced dipole interaction > induced dipole - dipole interaction > london force

So, ion-dipole interaction is stronger than hydrogen bonding.

Hence, the interaction between sodium ion and the partial negative charge on the oxygen is stronger.