Concept:Organic solids like ethanedioic acid are purified by crystallisation, which uses differences in solubility to separate pure crystals from impurities.
Explanation:Ethanedioic acid is a solid.
Impure solids are best purified by dissolving them in a hot solvent and then cooling the solution slowly.
When the hot solution cools, pure crystals of ethanedioic acid form and separate out.
The soluble impurities remain dissolved in the mother liquor.
The crystals are then filtered and dried to obtain the purified solid.
Distillation is for liquids, while decantation and filtration only separate insoluble solids from liquids.
Answer:C. crystallisation