Percentage of Water in a Hydrate
Purpose:
In this experiment you will find out how much water is associated with hydrated crystals. You should use a reference book to learn more about the activity of hygroscopic crystals and the expected masses of the hydrated compounds.
Water of hydration can be driven off by the application of heat. From a weighed mass of hydrated crystal you need to subtract the mass of the anhydrous crystal. This will give you the amount of water driven off. You will then find the percentage of water in the hydrated compound. Using the information from the reference book you will determine the theoretical percentage of water and determine the percent error.
Materials:
- bunsen burner or propane torch
- crucible with cover OR pyrex testube
- balance
- tongs or pliers
- one or more of the following compounds: alum, Borax,
FeSO4. 7 H2O,
Mg(NO3)2. 6 H2O,
MgSO4. 7 H2O,
Na2CO3. H2O,
SrCl2. 6 H2O,
Fe(NO3)3. 9 H2O,
Zn(NO3)2. 6 H2O,
Cu(NO3)2. 3 H2O.
Procedure:
- Put on goggles, apron and follow safety precautions on the MSDS sheets.
- Handle the testube or crucible and cover with tongs or pliers.
- Weigh the empty crucible and cover or open testube.
- Weigh the hydrated crystal in the crucible with the cover on or in an open testube.
- Move the crucible with tongs or pliers to where it will be heated.
- Heat until no more moisture is apparent. If a testube is used the opening should be pointed toward the wall and away from where people may be located.
- Allow the crucible, contents and cover to cool before weighing.
- Repeat the heating and cooling steps followed by reweighing. The weight should be constant if all the moisture is removed.
- Dispose of chemical properly.
Discussion:
- Determine the percentage of water in the hydrated crystal.
- Determine the percent error.
- If results are off by more than _____percent give an explanation as to what happened that was not expected.
- How can silica gel and other dessicants that have become wet be revived to continue to remove water from their surroundings?
- Name two acids that are hygroscopic.
- What percent is the average vapor pressure of water compared to standard atmospheric pressure?
In this experiment you will find out how much water is associated with hydrated crystals. You should use a reference book to learn more about the activity of hygroscopic crystals and the expected masses of the hydrated compounds.
Water of hydration can be driven off by the application of heat. From a weighed mass of hydrated crystal you need to subtract the mass of the anhydrous crystal. This will give you the amount of water driven off. You will then find the percentage of water in the hydrated compound. Using the information from the reference book you will determine the theoretical percentage of water and determine the percent error.
FeSO4. 7 H2O,
Mg(NO3)2. 6 H2O,
MgSO4. 7 H2O,
Na2CO3. H2O,
SrCl2. 6 H2O,
Fe(NO3)3. 9 H2O,
Zn(NO3)2. 6 H2O,
Cu(NO3)2. 3 H2O.
- Put on goggles, apron and follow safety precautions on the MSDS sheets.
- Handle the testube or crucible and cover with tongs or pliers.
- Weigh the empty crucible and cover or open testube.
- Weigh the hydrated crystal in the crucible with the cover on or in an open testube.
- Move the crucible with tongs or pliers to where it will be heated.
- Heat until no more moisture is apparent. If a testube is used the opening should be pointed toward the wall and away from where people may be located.
- Allow the crucible, contents and cover to cool before weighing.
- Repeat the heating and cooling steps followed by reweighing. The weight should be constant if all the moisture is removed.
- Dispose of chemical properly.
- Determine the percentage of water in the hydrated crystal.
- Determine the percent error.
- If results are off by more than _____percent give an explanation as to what happened that was not expected.
- How can silica gel and other dessicants that have become wet be revived to continue to remove water from their surroundings?
- Name two acids that are hygroscopic.
- What percent is the average vapor pressure of water compared to standard atmospheric pressure?
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