Question

In one trial of this experiment, significant impurities were detected in the extracted caffeine. Based on the results of the experiment, which of the following would be the expected melting point range for this extracted sample? (pure caffeine has a melting point of 235°C)

A. 195°C-220°C
B. 245°C-267°C
C. 233°C-236°C
D. 190°C-195°C

Answer 1

Impurities in a substance cause the melting point to decrease, so the expected melting point range for an impure caffeine sample, with pure caffeine having a melting point of 235°C, would be A) 195°C-220°C.

Step-by-step explanation:

The question involves understanding the concept of melting point depression due to impurities in a sample. Pure substances have a specific melting point, while impurities cause the melting point to be lower and over a broader range. Given that the pure caffeine has a melting point of 235°C, if significant impurities were detected in a caffeine sample extracted from coffee beans, we would expect the melting point range of the impure caffeine to be lower than the melting point of pure caffeine.

Therefore, the correct answer would be A. 195°C-220°C. Impurities disrupt the regular lattice structure of a crystalline substance, which results in a decreased melting point and a broader melting point range.