Question

You work in an analytical laboratory and you are asked to prepare 250 mL of a 0.5 M stock solution of anthracene with toluene as the solvent. The density of toluene is 0.87 g/mL. You look up the molar mass of anthracene, which is 178.2 g/mol. To prepare the solution, you weigh 22.3 g of anthracene and put it into a 250 mL volumetric flask. Then, you fill the flask to the mark with toluene. However, even after several hours of intensive stirring, there is still a substantial portion of undissolved anthracene in the flask. This is surprising because you would expect these two aromatic compounds to form a near-ideal liquid mixture. Why is the solid not dissolving? Also, provide an estimate of how much anthracene has actually been dissolved in grams. Additionally, what is the anthracene concentration in the stock solution in molar units at 20°C? The necessary data can be found in Appendix C. Anthracene: MW = 178.2 g/mol Melting point: 341°C Boiling point: 217.5°C

          You work in an analytical laboratory and you are asked to prepare 250 mL of a 0.5 M stock solution of anthracene with toluene as the solvent. The density of toluene is 0.87 g/mL. You look up the molar mass of anthracene, which is 178.2 g/mol. To prepare the solution, you weigh 22.3 g of anthracene and put it into a 250 mL volumetric flask. Then, you fill the flask to the mark with toluene. However, even after several hours of intensive stirring, there is still a substantial portion of undissolved anthracene in the flask. This is surprising because you would expect these two aromatic compounds to form a near-ideal liquid mixture. Why is the solid not dissolving? Also, provide an estimate of how much anthracene has actually been dissolved in grams. Additionally, what is the anthracene concentration in the stock solution in molar units at 20°C? The necessary data can be found in Appendix C.

Anthracene:
MW = 178.2 g/mol
Melting point: 341°C
Boiling point: 217.5°C

Added by Karen B.

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