A forensic chemist is given a white powder for analysis. She dissolves 0.50 g of the substance

Question:

A forensic chemist is given a white powder for analysis. She dissolves 0.50 g of the substance in 8.0 g of benzene. The solution freezes at 3.9°C. Can the chemist conclude that the compound is cocaine (C17H21NO4)? What assumptions are made in the analysis?