is this right?
5. After heating the crucible is set on the lab bench where it is contaminated with the cleaning oil used to clean the lab bench but before its mass is measured. The analysis continues where the mass of the anhydrous salt is determined. While heating, the cleaning oil is burned off the bottom of the crucible. Describe the error that has occured; that is, is the mass of the anhydrous salt remaining in the crucible reported as being too high or low? Explain.
The mass of the anhydrous salt is too low because steam and some of the oil was boiled off. And, the errors increase because you are not able to separate the steam and anhydrous salt.
what else could i add?
I agree with part of the first sentence but not the second. The water is boiled off too so it is separated about as much as you could want. For the first sentence, don't you want the water to be boiled off and that is the reason you get the remaining anhydrous salt. In fact, if the xble was not contaminated with the oil you would lose the H2O normally and the difference in mass is the mass of the H2O driven off and leaves the anhydrous salt as it should be.
In addition to the mentioned errors, there are a few more aspects that you could consider adding to your explanation:
1. Evaporation of volatile compounds: When the crucible is heated, not only does the cleaning oil burn off, but it is also possible for some volatile compounds present in the anhydrous salt to evaporate. This evaporation can result in a loss of mass, leading to a lower measured mass of the anhydrous salt.
2. Contamination from cleaning oil: The cleaning oil used on the lab bench can contaminate the crucible, introducing impurities that could affect the accuracy of the analysis. These impurities may contribute to an increased measured mass of the anhydrous salt.
3. Incomplete removal of cleaning oil: Even if the cleaning oil burns off during heating, there is still a chance that some residue may remain on the crucible. This residue can contribute to an increased measured mass of the anhydrous salt.
4. Condensation of water vapor: As the crucible cools down after heating, any steam that was generated from the heating process may condense and reattach to the anhydrous salt or the crucible. This condensation can introduce additional mass, resulting in an increase in the measured mass of the anhydrous salt.
By mentioning these additional factors, you provide a more comprehensive explanation of the potential errors that can impact the accuracy of the reported mass of the anhydrous salt.