is this right?

Question

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?

Answer 1

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.