Determining the Chemical Formula of a Hydrate

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Determining the Chemical Formula of a Hydrate
Chemistry 11
3/5/2013

Purpose: To determine the percent by mass of water in a hydrate of copper (II) sulfate hydrate.  Hypothesis: I hypothesize that when the solution is heated the hydrate will convert to an anhydrous ionic compound. Then the percentage composition will be determined by weighing the mass of the white crystals.

Materials: 400ml beaker, hot plate, tongs, scoopula, electronic balance, glass rod, hot pad, and 4g of hydrated copper (II) sulfate
Procedure:
1. Measure the mass of the beaker and stirring rod.
2. Add 4g hydrated copper (II) sulfate to the beaker.
3. Measure the mass of the beaker with the hydrated copper (II) sulfate 4. Heat the beaker with the hydrated copper (II) sulfate until the crystals lose their blue color. Stir occasionally with the glass rod while keeping the heat at a medium setting. 5. When the color changes stop heating the beaker and turn off the hot plate. Remove the beaker. Allow the beaker and crystals to cool on a hot pad. 6. Return the anhydrous copper (II) sulfate to its container. Do not put in sink or garbage.

Conclusion: The experiment showed that the percent water in a hydrate can be found by carefully heating the hydrate to drive off the water. Some of the hydrated copper (II) sulfate was light brown, which is an indication of excess heating. Excess heating could result in decomposition of the copper (II) sulfate. Decomposition of the copper (II) sulfate would lead to greater apparent water loss. That would explain the slightly high values
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