Question

A compound melting at 134 degree C was suspected to be either aspirin (mp 135 degree C) (mp 133 degree). Explain how you could whether or urea identical to determine one of these two suspected was the unknown compound without using any form of spectroscopy. An unknown compound gave a melting point of 230 degree C. When the molten liquid solidified, the melting point was redetermined and found to be 131 degree C. Give a possible explanation for this discrepancy.

Answer 1

To identify whether an unknown compound is aspirin or urea, execute a mixed melting point test using known samples of both substances. A sharp melting point corresponds to purity, while a broader range suggests a mixture. The discrepancy in melting point after resolidification could indicate decomposition or measurement error.

Step-by-step explanation:

To distinguish between aspirin and urea as the unknown compound with a melting point of 134 degrees Celsius, you would perform a mixed melting point test. This involves mixing a small amount of the unknown compound with a known sample of aspirin and a separate mixture with a known sample of urea.

You then measure the melting point of these mixtures. If the melting point of the mixture significantly deviates from the known pure substance, it suggests the unknown compound is not identical to the known one, indicating a mixture of different compounds. Pure substances have a sharp melting point, while mixtures of two different compounds have a lowered and broader melting range. The discrepancy in the melting point of the unknown compound from 230 degrees Celsius to 131 degrees Celsius after resolidification could be due to Decomposition, contamination, or an initial error in measuring the melting point before the substance had completely melted.