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Hey everyone!  I was hoping someone could help me with a question I have.  We did a gravimetric determination of chloride percentage in an experiment.  We obtained the precipitate AgCl at the end which helped us to determine the % of Cl in the unknown, according to the equation Ag + Cl -> AgCl.  I understand how to find the weight percentage of Chloride, but am stuck on how to report the uncertainty.

Show a calculation of the weight % Cl, with its uncertainty

Well, we first had to measure crucibles, then at the end we weighed the crucibles with the AgCl precipitates inside.  That would count as 2 uncertainties, and the analytical balance uncertainty is 0.0002g so it would be (0.0002^2 + 0.0002^2)^(.5)=0.0003g.  We weighed the unknown once, which would be 0.0002g uncertainty, and this is when I got confused.  Any help would be appreciated.