Experiment 5: Percent Water in a Hydrated Salt

Chemistry 1300
Instructor:
2/8/12

Abstract:

The purpose of this experiment was to determine the percent by mass in a hydrated salt, as well as to learn to handle laboratory apparatus without touching it. The hydrated salt, calcium carbonate, was heated with high temperature to release water molecules. Gravimetric analysis was used in this experiment to determine the percent by mass of water in a hydrated salt. The hypothesis of this experiment was accepted on the basis that the percent by mass of volatile water in the hydrated salt would be fewer than 30%. The percent by mass was determined by the mass of water loss devised by the mass of hydrated salt multiplied by total capacity …show more content…

Mass of a hydrated salt (g) = (Mass of fired crucible, lid, and hydrated salt (g)) – (Mass of fired crucible and lid (g)) = 45.720g – 42.679g = 3.041g

2. Mass of anhydrous salt (g) = (Mass of crucible, lid, and anhydrous salt (g)) – (Mass of fired crucible and lid (g)) = 45.083g – 42.679g = 2.404g

3. Mass of water loss (g) = Mass of the hydrated salt (g) – Mass of the anhydrous salt (g) = 3.041g- 2.404g = 0.637g

4. Percent by mass of volatile water in hydrated salt (%)= Mass of water lost (g) / Mass of hydrated salt (g) x 100 = (0.637g/ 3.041) x 100 = 20.9%
Discussion:
The purpose of this experiment was to determine the percent by mass in a hydrated salt, as well as to learn to handle laboratory apparatus without touching it. A hydrated salt calcium carbonate (CaCO3) was utilized for this experiment because the water molecules are weakly bonded to the ions allowing heat to remove them and form an anhydrous salt. As the sample was heated a second time, more water molecules were released, demonstrating the sample decomposable. Table 1 was used to determine the mass of the hydrated salt, the anhydrous salt, and the water loss. The calculations were determined using the gravimetric analysis resulted in table 2 cells B6, C6, and D6. The mass of the fired crucible and lid along with 3 grams of the CaCO3 were weighed. As the sample was repeatedly heated more water molecules were lost each time decreasing the grams in weight for each recording. The