Driving Question: How can you use gravimetric analysis to obtain the formula of an unknown sulfate sample?
The purpose of this lab was to use gravimetric analysis to obtain the formula of an unknown alkali sample. By obtaining the mass of the precipitate when filtered and dry, the sulfate content can be calculated and the unknown sample can be found.
Gravimetric analysis is one of the oldest and most accurate quantitative methods for determining the amount of an analyte in a sample. This is done by transforming the analyte into a water insoluble form which the precipitate can be isolated from the solution by filtration. The final stage would be to obtain the mass, and from that determine the percentage of sulfate content in the precipitate. In this lab it begins by obtaining the unknown sample, measuring it, and dissolving it in dilute hydrochloric acid. The sample is then isolated by precipitation with barium chloride and heated to form particles. The precipitate is collected by filtration, and heated until there is no carbon residue left, then the mass is measured. The number of moles and percentage of sulfate content can be found after, along with what the unknown sample could be.