Final answer:
A lower experimental melting point of acetanilide compared to the literature value may indicate the presence of impurities in the sample or an error in the heating method used for measurement.
Step-by-step explanation:
If an experimental melting point of acetanilide is lower than the literature value, several factors could be responsible. One potential reason is the presence of sample impurities, which generally cause the melting point of a substance to decrease, as the impurities disrupt the regular structure of the crystalline solid making it easier to melt. This is supported by principles observed in other substances, such as when a small amount of Al2O3 is mixed with Na3AlF6, leading to a lower melting point, facilitating aluminum production. A high purity sample typically would not show a significantly lower melting point unless there were errors in the measurement method. Therefore, a potential error with the heating method used to determine the melting point could also be a cause for the discrepancy; if the heating rate was too rapid or uneven, it could affect the observed melting point.