Gravimetric Determination of Sulfate
Eisman E. Morales
TA: Jackeline Pennywiit
To determine the percent sulfate in a sample using a semimicro scale gravimetric procedure.
Refer to pages 41-42 of General Chemistry volume 1 Laboratory Experiments by Judith Casey and Robert Tatz, Hayden McNeil Publishing, 2010
See attached report sheet.
1. Explain how your calculated value for percent sulfate would be affected if:
a. Insufficient BaCl2 is added.
In the case that insufficient BaCl2 would be added, some SO4 (sulfate) molecules from the sample would have remained in the solution without precipitating and therefore, a smaller than the actual amount of sulfate would have been determined.
b. Addition of acid is omitted.
If no acid would have been added, some BaCO3 would have formed along with BaSO4 giving us a higher amount of precipitate and we would have ended up calculating a larger than the actual amount of sulfate.
d. Some solid is withdrawn with the wash water.
Taking out some solid gives us less amount of precipitate in the test tube and this would have mislead us to calculate a smaller amount of sulfate in the sample.
4. A 0.0583 g sample of cerium sulfate was dissolved in dilute HCl and treated with 10% BaCl2 solution. The BaSO4 precipitate weighed 0.0839 g. Determine the formula of this sulfate of Cerium (no. 58)
In this experiment we could determine the percent sulfate in a sample using semimicro scale gravimetric procedure. First by weighing the sample before starting we knew how much unknown substance we had. Then by mixing it with distilled water we made a solution in which we had a precipitate after adding 1 to1.5 ml of Barium Chloride. We also added HCL 1M before BaCl2 to eliminate the chance of formation of another precipitate such BaCO3. Then we extracted the supernatant liquid and dried...