CHEM QUESTION

For questions about solubility, we often apply "like-dissolve-like" principle, i.e. when two substances have the same or similar strength of intermolecular forces, it is likely to be soluble.

This is because when two substances share same intermolecular force, the strength of inter-species and intra-species intermolecular forces are similar. Therefore, they can be mixed easily, i.e. Dissolved. When two substances have huge difference in strengths of intermolecular force, the substance with stronger intermolecular force can hardly be separated, i.e. NOT Dissolved.

Specify to your situation, ethyl ethanoate molecules are held together by Van der Waal's force, while that of iodine and sodium iodide are Van der Waal's force and strong ionic bond respectively. Therefore, ethyl ethanoate share same intermolecular force with iodine but not with sodium iodide.

As a result, ethyl ethanoate can dissolve iodine but cannot dissolve sodium iodide.

I'm not really sure...

Ethyl ethanoate is a non-aqueous solvent. That means it does not contain any water molecules. The difference between iodine and sodium iodide is that one is Molecule, one is Ionic Compound.

Structure of molecules:
Discrete molecules are held to each other by weak van der Waal's forces. This means that the molecules can be easily separated by non-aqueous solvents.

Ionic Compounds:
Ionic compounds, on the other hand, are held by strong ionic bonds. These bonds cannot be overcome by non-aqueous solvents, but most of them can dissolve in water.

Which is why ethyl ethanoate can dissolve iodine(comparatively weaker in terms of bonding between separate molecules), but not sodium iodide(stronger bonding exists in compounds).

Like dissolve like....