Answer:
to remove any remaining 2,4-dinitrophenylhydrazone
Step-by-step explanation:
Usually, when an organic compound is synthesised, traces of impurities such as excess reagents or solvent remain in the product.
It is therefore imperative that these contaminants are removed so that the product can attain a very high degree of purity.
Hence, during the synthesis of 2,4-dinitrophenylhydrazone derivative, 10 mL of 2 M hydrochloric acid is titrated against the crude product so that any remaining 2,4-dinitrophenylhydrazone is removed.