Pure acetylsalicylic acid has a melting point of 135.0 - 135.5 (degrees Celsius). What would you expect for the melting point is this was mixed as a 50:50 mixture with pure benzoic acid (melting point 121 - 122)? Explain.
Hmmm. 50:50 on mole basis or mass basis?
I'm assuming mass? I'm not sure.
The melting point would depress because the solution would be impure.
To determine the expected melting point of a mixture of two substances, we need to consider their individual melting points and the interaction between the two compounds.
In this case, we have a mixture of pure acetylsalicylic acid and pure benzoic acid. Acetylsalicylic acid has a melting point of 135.0 - 135.5 °C, while benzoic acid has a melting point of 121 - 122 °C.
When two substances are mixed, they can form a eutectic mixture, resulting in a lower melting point than the individual melting points of the pure compounds. This occurs because the interaction between the molecules in the mixture disrupts the crystal lattice structures of the pure compounds.
In our case, since we have equal proportions of acetylsalicylic acid and benzoic acid (a 50:50 mixture), it's likely that a eutectic mixture will form. The eutectic mixture is expected to have a melting point lower than the pure compounds.
Without knowing the exact eutectic composition, it's challenging to precisely predict the exact melting point of the mixture. However, it is reasonable to expect that the melting point of the 50:50 mixture of acetylsalicylic acid and benzoic acid will be lower than 135.0 - 135.5 °C, possibly closer to the range of 121 - 122 °C or somewhere in between.
To obtain a more accurate prediction, one would need to consult published phase diagrams or conduct experimental measurements to determine the exact composition and the corresponding melting point of the eutectic mixture.