Lab Report: Percentage Of Water In A Hydrate

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CHEMISTRY September 25, 2010 Experiment #5: Percentage of water in a Hydrate Summary of Principles In this lab, students will calculate the amount of water in an unknown hydrate. A hydrate is a compound with a specific number of water molecules associated with the ions of that compound. A hydrate may form when an anhydrous compound is exposed to atmospheric water or when the ionic compound is crystallized from an aqueous solution. An anhydrous compound is a substance without water. There are two parts to this lab. Part 1 which will be a known hydrate CoCl2 ∙6H2O or Cobalt (II) Chloride hexahydrate, and Part 2 which will be an unknown hydrate. Equations and Mechanisms * Moles of hydrate and water ratio: Moles of water Moles…show more content…
First obtain 2 crucibles and lids. Label them #1 and #2. Make sure to clean the crucibles thoroughly. Now for part 1; weigh the crucible without the hydrate before heating. Then weigh the crucible without the hydrate after heating. Record both masses. Next, add CoCl2 ∙6H2O and weigh the crucible. Now place the hydrate and crucible on the hot plate. Observe the color change while it is being heated. After observing the color change, find the mass and moles of the hydrate. Then find the mass and moles of the water eliminated. And lastly find the mole ratio of water to hydrate. For part 2, do the same thing as part 1 except use an unknown hydrate and calculate the percent mass of water in an unknown hydrate. Observations Part 1 At first the hydrate was a crystal red color. When it was placed on the hot plate and its state changed it began to change color. As it heated it started to become liquidly and bluish in color. Once it cooled down it became a purplish black color. Part 2 The unknown hydrate was first a blue powder. Starting at 75C there was barely an white edge. But as the temperature increased to 275C the blue became lighter and lighter, until there was barely any blue left. Results and…show more content…
An error that could have occurred is that the students did not leave the crucible on the hot plate long enough for the color to change. Another error could have been that the temperature was not hot enough. In order to correct these errors, the students would need enough time to do the experiment thoroughly and would also need to check the temperature on the hot plate. References: Deng, Yuanjian, and Sapp, John B. General Chemistry Laboratory Fifth Edition. Texas: Fountainhead Press, 2006

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