Gravimetric determination of Calcium

Gravimetric determination of Calcium

  • Submitted By: ishruales
  • Date Submitted: 09/05/2014 10:35 AM
  • Category: Science
  • Words: 359
  • Page: 2

Sample No.
Volume of sample analyzed, ml
Weight of petridish + filter paper, g
Weight of CaO precipitate, g
Weight of Ca in CaO precipitate, g
Average weight of Ca in CaO precipitate, g

25.00 ml
43.8369 g
0.6446 g
0.4607 g

25.00 ml
32.4056 g
0.6062 g
0.4332 g
0.4851 g

25.00 ml
42.4612 g
0.7851 g
0.5615 g

Gravimetric analysis is a method used in analytical chemistry for a quantitative analysis of an
analyte by weighing its mass as a solid. The two types of gravimetric analysis are by 1) Precipitation and
2) Volatilization.
In the experiment, the students performed gravimetric analysis by precipitation. The students
were able to learn that weight of Calcium can be determined with Calcium oxalate dihydrate. The
students prepared an unknown solution diluted in 0.1M HCl solution with Methyl red as an indicator,
Ammonium oxalate solution, and Urea. By adding ammonium, this causes all Calcium to precipitate as
Calcium oxalate dihydrate. From there, thermal decomposition of Urea must occur (hence, use and
exposure to heat) resulting to gradual raise in pH (hence, use of Methyl red as an indicator) to Ca+2 and
C2O4-2 to dissolve. This process converts the precipitate to CaO entirely. This is then filtered after
cooled, and the filtrate is then weighed and CaO can be determined. Using appropriate gravimetric
factors, Ca is determined too using stoichiometry.

The students would strongly recommend that weighing must be done with extreme focus and
must be done in a controlled room to avoid errors. The experiment is time-consuming, therefore,
tabulating the flow of procedure is highly recommended so as not to get lost in performing the
experiment. The students suggest that vigilance must be practiced in observing changes in color of
solution being analyzed since the experiment also deals with indicators because a...

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