Ap Chemistry - Gravimetric Lab Essay Example for Free

Ap Chemistry Gravimetric Lab Essay By filtering and weighing the carbonate after it has precipitated, the mass and moles of CaCO3 could then be found; with these values, a molar mass of M2CO3 can be found. Using gravimetric analysis, it has been determined that the unknown Group 1 metal carbonate compound is K2CO3 (potassium carbonate). Experimental Sources of Error: A) The first source of error had to do with the precipitation section of the lab. Not only is possible, but it is almost guaranteed that the CaCO3 did not precipitate to its fullest extent. Attaining a precipitate that is 100% pure and is exactly of the composition represented by its chemical formula would be extremely difficult. A second source of error was in the filter paper. No filter paper can be perfect, and it is very likely that it did not filter all of the precipitate, which would then decrease not only the mass of CaCO3, but also the molar mass because only the majority of the correct mass of the precipitate was found; by lowering the mass of a compound, its molar mass will also fall. B) After the precipitate had been filtered and dried, the filer paper that contained the precipitate was mishandled and its contents was scattered all over our lab bench. The dried precipitate had to be then gathered and then put back onto the filter paper; this contributed a large portion of human error to this lab. Spilling the dried precipitate is a source of human because it is almost guaranteed that not all of the precipitate was collected that had been spilled. This would have then lowered the mass of all of the following data, and wholly, our end result (i.e. molar mass). C) Percent error = your result-accepted valueaccepted value x 100 Percent error = 128.79-138.21138.21 x 100 = 6.8157% Considering that any percent error that is under 5% is often times considered accurate, a percent error of 6.8% can be viewed as fairly accurate. It is not too far off to completely disregard, but it is also not close enough to use as fact.