In lab, we purified acetanilide through recrystallization. We did not have have time to test the melting point to check the purification, so we put the recovered crystals in a 50ml beaker, covered the top with parafilm with a few holes poked in the top, and left them for the next lab. When we left, everyone had crystals in their beakers. When we returned a week later, only one group had crystals left in their beakers. How could this have happened? The beakers were not messed with by any other class or person working in the lab. Any thoughts?
There could be several reasons why only one group had crystals left in their beakers while others did not. Here are a few possibilities:
1. Humidity: If the lab environment had high humidity, it could have caused moisture to enter the beakers and dissolve the crystals. The group that still had crystals may have sealed their beaker more effectively, preventing moisture from entering.
2. Evaporation: If the beakers were not covered tightly enough, the solvent used for recrystallization could have slowly evaporated over time, causing the crystals to dissolve. The group that had crystals may have covered their beaker more securely.
3. Temperature: If the lab temperature fluctuated significantly, it could have affected the solubility of the compound. For example, if the lab became warmer, the compound might have become more soluble, causing the crystals to dissolve. The group that had crystals may have stored their beaker in a cooler location.
4. Contamination: It's possible that some form of contamination affected the beakers of the other groups. This could have been due to impurities in the water used for recrystallization or other factors. The group that had crystals may have had cleaner starting materials or used better purification techniques.
It's important to note that without further information or investigation, it is difficult to determine the exact reason why only one group had crystals left in their beakers.
Based on the given information, here are a few possible explanations for why only one group had crystals left in their beakers:
1. Temperature fluctuations: If the room temperature varied significantly during the week, it could have impacted the stability of the acetanilide crystals. Acetanilide has a melting point of around 114 degrees Celsius, so if the temperature in the room exceeded this point, the crystals could have melted.
2. Moisture absorption: Acetanilide has hygroscopic properties, which means that it can absorb moisture from the surrounding environment. If the room had high humidity or the beakers were improperly sealed, the crystals may have absorbed moisture from the air and dissolved, leading to loss of crystallinity.
3. Contaminants and impurities: If the acetanilide crystals were not properly purified and still contained impurities, these impurities could have played a role in the loss of crystallinity. Impurities can disrupt the crystal lattice structure and make the crystals more prone to dissolution.
To determine the exact reason for the disappearance of the crystals, it would be necessary to conduct some further investigations. It is recommended to perform a melting point test or use other analytical techniques to confirm the identity and purity of the recovered crystals. This will help in assessing whether the recrystallization process was successful and provide more insights into the observed phenomenon.