Mass of the dried precipitate from the mass of the empty crucible and the mass of the crucible with the dried precipitate:
37.8356 g - 37.1929 g = 0.6427 g
The number of moles of precipitate from its mass and formula weight:
0.6427 g x 1 mol BaSO4 = 0.0028 mol BaSO4
1 233.4 g BaSO4
The number of moles of sulfate ions in the precipitate from the number of moles of precipitate:
0.0028 mol SO42-
The moles of SO42- are equal to the moles of BaSO4.
The mass of the sulfate ions form the number of moles of sulfate ions:
0.0028 mol x (96.1 gSO42-) = 0.26898 g SO42-
(1 mol SO42-)
The theoretical percentage of sulfate content in the unknown sulfate sample based on the mass of the sulfate ions and the total mass of the sample:
(0.26898 g SO42-) x 100 = 76.9%
(0.35 g)
The percent error based on the experimental value of the percent sulfate content of the sample and the percent sulfate content of the proposed unknown:
(79.806 % MgSO4 – 76.9 % SO42-) x 100 = 3.78% error
(76.9% SO42-)