The Gravimetric Stoichiometry Lab was a two-week lab where we tested one of the fundamental laws of chemistry; the Law of Conservation of Mass. The law states that in chemical reactions, when you start with a certain amount of reactant, the product should theoretically have the same mass. This can sometimes be difficult because in some reactions gases are released and it is difficult to measure the mass of a gas. Some common gases released in chemical reactions include hydrogen, carbon dioxide, oxygen, and water vapor. One of the best methods for determining mass in chemistry is gravimetric analysis (Lab Handout). This is essentially using the mass of the product to determine the original mass we are looking for. Therefore the purpose of our experiment was to compare the final mass of our reaction to the initial mass and determine the change in mass. In our experiment we used hydrated cobalt chloride. Hydrates are crystalline compounds in which one or more water molecules are combined with each salt unit. Cobalt(II) chloride hexahydrate is an inorganic compound that is deep pink in color in its hydrated form. As an inducer of our procedure, however, it was not free from errors. These errors are vital because they affect the data we conclude. Theoretically, according to the balanced chemical equation, for each mole of hydrated cobalt chloride that is heated, the decomposition ensures that the compound decomposes into one mole of cobalt(II) chloride and six moles of gaseous water vapor. So, in theory, in each test we should lose a mass equal to six moles of water vapor. Unfortunately, this is not the case because we do not have perfect laboratory conditions and factors such as heating time, using the same crucible, and inconsistency in Bunsen burner flame size all contribute to differences in mass percent change. for each