The Gravimetric Determination of Sulfate
November 14, 2012
The purpose of this experiment was to perform gravimetric analysis to quantitavely determine the amount of the sulfate ion in an unknown sample and compare individual results with an aggregated group sample by applying statistical methods.
Gravimetric analysis is a process by which the compound of interest (analyte) is precipitated as an insoluble compound and weighed . In this experiment, the analtye BaSo4 was used due to its ability to form a solid, rather than an aqueous product. If volumetric determination of the analyte is provided, then the following steps can henceforth be used in gravimetric analysis. First,…show more content…
The experiment was divided into two parts: Part I, Determination of percent sulfate and Part II, statistical calculation of data. First, a clean, dry watch glass was weighed to the nearest .001g and recorded. Approximately .800g of an unknown sample was placed on the watch glass, with weight recorded. The unknown sample was then transferred to a 400-mL beaker. The watch glass was rinsed of remaining particulate using deionized water into the same beaker. An additional 200-mL of deionized water was poured into the beaker, followed by 2 mL of concentrated HCl. The beaker was stirred with a glass rod until thoroughly mixed.
A ring stand fixed with an iron ring and wire gauze was placed over a Bunsen burner. The beaker containing the solution was placed on the wire gauze and slowly heated to nearly the boiling point. Twenty-five mL of a .3M BaCl2 solution was placed in a graduated cylinder and agitated while slowly adding small droplets of the heated solution to the cylinder. Stirring was continued until a visible precipitate (BaSO4) was formed.
The precipitate was heated continuously for 30 minutes over a medium flame and monitored for clarity. Once clear in appearance, the flame was extinguished and the solution cool before being removed from the wire gauze and contained. A plastic funnel was placed in the ring stand while a 250-mL beaker was sat underneath. A funnel was constructed