Lab-report 4 - Calculation of Mass Percentage of Water in Unknown Hydrate PDF

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Calculation of Mass Percentage of Water in Unknown Hydrate...

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RCC- Inorganic Chemistry

Lab #4

Cecilia Pantua-Evasco

Title: Calculation of Mass Percentage of Water in Unknown Hydrate Materials: crucible with cover, Bunsen burner, support ring, ring stand support, clay triangle, metal tongs, flint striker, unknown hydrate sample, analytical balance. Procedure: The crucible was prepared, fired, and weighed for initial mass after it cooled down. The setup is depicted in the photo below.

An unknown hydrate (B) was then added to the prepared crucible then weighed for mass data. Physical characteristics of unknown hydrate were recorded. Next, the crucible with the unknown hydrate was fired for several minutes with its lid left slightly ajar. After cooling down the crucible with its lid covered, the mass of the anhydrous salt was weighed and the data recorded. The process of heating the anhydrous salt was repeated several times until two masses of the sample weighed almost the same to indicate complete dehydration. Physical characteristics of anhydrous salt were noted and recorded. Observations: The unknown hydrate turned a different color: yellowish, sage green from its original color of lime green. The anhydrous salt was clumped in powdery like resin. The weight of the anhydrous salt was noticeably less than in its original form as a hydrate. The changes depicted are revealed in the data chart below.

Conclusion: The data collection yielded a final mass of 1.22 g for the unknown anhydrous salt. Based on the formula given to determine the percentage of water content of a substance (mass of water in hydrate divided by final mass of unknown multiplied by 100), the mass water percentage in the original unknown hydrate was 59.09%. It can be concluded that, hydrate compounds lose water molecules through heating and absorb back water molecules when added. Sprinkles of water added to the anhydrous salt allowed it to become a hydrate again after a few minutes of wait time. Also, when an unknown hydrate has become dehydrated, its physical appearance changes as demonstrated by the change in color from lime green to yellowish sage green in the unknown substance used for this lab....