A student who was isolating aspirin stopped the experiment after filtration step alumina. One week later, the methanol was evaporated and the experiment was completed. The melting point of the aspirin was found to be 110-115 degrees C. Explain why the melting point was low and why the melting point was so wide.

thanks in advance

A range of more than about 1-2 degrees plus the melting point being lowers means there is one or more impurities in the final product.

The low melting point of the aspirin could be due to impurities present in the sample. Aspirin is expected to have a melting point of around 135-140 degrees Celsius. However, impurities or incomplete synthesis can lower the melting point.

In this case, the student stopped the experiment after filtration with alumina. Alumina is commonly used in column chromatography to separate compounds, as it selectively adsorbs impurities while allowing the desired compound to pass through. By stopping the experiment at this step, it is possible that some impurities remained in the aspirin sample, leading to a lower melting point.

Additionally, the wide range of the melting point (110-115 degrees Celsius) indicates a mixture of different compounds present in the sample. This could be a result of incomplete purification or synthesis, as well as impurities introduced during the experiment.

In summary, the low melting point and wide range observed in the aspirin sample could be attributed to impurities and incomplete synthesis or purification processes.

The low melting point of the aspirin and the wide melting point range could be due to several factors. Let's break it down:

1. Incomplete drying: In this case, the student stopped the experiment after the filtration step with alumina. However, methanol was still present in the aspirin sample. Methanol has a boiling point of around 65 degrees Celsius, which is significantly lower than the reported melting point range of 110-115 degrees Celsius. Therefore, the presence of residual methanol can lower the melting point of the aspirin.

2. Impurities: Impurities in the aspirin sample can also affect its melting point. If there are impurities present, they can disrupt the orderly arrangement of molecules in the solid structure, resulting in a lower melting point. Additionally, impurities can cause a broader melting point range by introducing different compounds with varying melting points.

3. Crystal size and shape: The size and shape of the aspirin crystals can influence the melting point range. If the crystals are larger or have irregular shapes, melting may occur over a wider temperature range than if they were uniformly sized and shaped. This is because different parts of the crystal structure may melt at slightly different temperatures.

To accurately determine the melting point of aspirin, it is important to ensure complete removal of any solvents, minimize impurities, and obtain a sample consisting of uniformly sized and shaped crystals.