Answer:
Na2SO4
Explanation:
Chemistry operates on the principle of 'like dissolved like'. This implies that polar solvents dissolve polar substances while nonpolar solvents dissolve nonpolar substances.
This is because, dissolution of a substance in a solvent is as a result of intermolecular interaction between solute and solvent.
Since Na2SO4 is purely an ionic substance and CCl4 is purely a nonpolar solvent, Na2SO4 is least soluble in CCl4.
