Predict a reasonable melting point of a mixture prepared by combining 25mg of biphenyl (mp=70-71C) with 75mg of acetyl salicylic acid (mp=138-140C). Answer should have temps in it.
To predict the melting point of a mixture, you need to consider the melting points of each individual component and their relative proportions. In this case, the mixture contains 25mg of biphenyl (mp=70-71°C) and 75mg of acetyl salicylic acid (mp=138-140°C).
To determine the melting point of the mixture, you can make an approximation using the concept of the "melting point depression." The melting point depression is based on the principle that when two or more substances are mixed, it can result in a lower melting point than the individual components alone.
To calculate the approximate melting point, you can consider the mass fraction of each component in the mixture. The mass fraction is calculated by dividing the mass of each component by the total mass of the mixture.
For biphenyl:
Mass fraction of biphenyl = mass of biphenyl / total mass of the mixture
= 25mg / (25mg + 75mg)
= 0.25
For acetyl salicylic acid:
Mass fraction of acetyl salicylic acid = mass of acetyl salicylic acid / total mass of the mixture
= 75mg / (25mg + 75mg)
= 0.75
Next, you need to determine the melting point range of the mixture. The melting point range is estimated by taking the weighted average of the melting points of the individual components using their respective mass fractions.
For biphenyl:
Melting point range of biphenyl = (upper melting point - lower melting point) x mass fraction of biphenyl
= (71 - 70) x 0.25
= 0.25
For acetyl salicylic acid:
Melting point range of acetyl salicylic acid = (upper melting point - lower melting point) x mass fraction of acetyl salicylic acid
= (140 - 138) x 0.75
= 1.5
Finally, you can estimate the melting point range of the mixture by adding the melting point ranges of the two components:
Melting point range of the mixture = melting point range of biphenyl + melting point range of acetyl salicylic acid
= 0.25 + 1.5
= 1.75
Therefore, you can predict that the reasonable melting point range of the mixture would be approximately 1.75°C.