It isn't clear as to when the sample is contaminated; i.e., before the original sample is weighed or after it is weighed.
a. If the sample is weighed, then contaminated, the %H2O in the hydrated salt will be unaffected. For example, say we take a sample, weigh it at 15 g, then contaminate with an unknown anhydrous salt (any amount). Upon heating it loses 10 g H2O so percent H2O is (10 g H2O/15 g sample)*100 = about 67%. No weights have changed and the anhydrous salt gives off no water so no harm done.
b. If the sample is contaminated BEFORE weighing the 15 g sample, then that 15 g is partly hydrated salt and partly anhydrous salt. Then %H2O = (loss in mass/15)*100 = ? But that loss in weight will be less (since there is less of the hydrated salt there) and the result will be low.
I also need help in this please:
Suppose the original sample is unknowingly contaminated with a second anhydrous salt. Will the reported percent water in the hydrated salt be too high, too low, or unaffected by its presence? Explain.
is it low? if so, can you explain in some detail because I'm not understanding.
thank you!
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