Final answer:
Crystallization is the most appropriate method to separate a mixture of benzoic acid and sodium nitrate.
Step-by-step explanation:
The most appropriate method to separate a mixture of benzoic acid and sodium nitrate is crystallization. Crystallization relies on differences in solubility between the components of a mixture. In this case, benzoic acid is more soluble in a particular solvent (such as water) compared to sodium nitrate. By dissolving the mixture in a suitable solvent and allowing it to cool, benzoic acid will crystallize out while sodium nitrate remains dissolved.