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3.09 Molar Mass of Compounds Honors

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alyssa zinn

on 16 May 2015

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Transcript of 3.09 Molar Mass of Compounds Honors

3.09 Molar Mass of Compounds Honors
By: Alyssa Zinn

The purpose of this experiment is to determine the formula of a copper sulfate hydrate by heating the sample until all of the water evaporates.
Data & Observation:
Discussion & Conclusion:
Heating the hydrate for the sufficient amount of time is very important in this experiment. First of all, the dehydrate mass will be higher than it is supposed to be. This is because the conductor of the experiment did not allow ample amount of time for the water to evaporate. Therefore resulting in a higher mass for the dehydrate. This would change the measure of the final mass because it can alter all of the steps after, which in turn result in miscalculations and and the miscalculations will then in turn result to a final answer that is not correct. To avoid this one must take time and set a timer, or carefully watch the experiment to make sure that the water in the hydrate is given a sufficient amount of time to evaporate.
All in all, during the lab I was able to conduct eriments to figure out the mass of the hydrate, then eva[porate the water in the hydrate and figure out the mass of the dehydrate. Which I was later able to perform calculations, such as turning the masses of the hydrate and dehydrate to moles, to figure out how many hydrates are in a Copper Sulfate Hydrate, so as a final result I was able to determine the formula as CuSO4*6H20.
Scale, Bunsen Burner, Hydrate, dehydrate, crucible, and a balance.
1. Measure the mass of the empty crucible and record the mass.
2. Fill the crucible about about 1/2 of the way full, or 4 scoops with the hydrate and record the mass.
3. Heat the crucible and hydrate above a Bunsen burner for at least ten minutes to make sure that all of the water evaporates.
4. Let the crucible cool and then measure the mass of the crucible with dehydrated solid inside, and record the mass.
5. Calculate the formula of the hydrate.
Mass, grams
Mass of empty crucible: 19.508g
Mass of crucible and hydrate: 40.117g
Mass of hydrate: 20.609g
Mass of crucible and dehydrate:39.720g
Mass of dehydrate: 20.212g

I also observed that when heating the hydrate, so it becomes the dehydrate, if one does not let it sit for the given amount of time, the mass is larger, and that can mess up a persons' entire experiment
1. Obtain the mass of the empty crucible. Obtain the mass of the crucible and the hydrate. Subtraction of the mass of the empty crucible from the mass of the hydrate and crucible gives the mass of the CuSO4 hydrate.
mass of hydrate
2. Heat the hydrate. After heating, record the mass of the crucible and the dehydrated compound.
3. Subtracting the mass of the empty crucible from the mass of the crucible and dehydrated CuSO4 gives you the mass of the dehydrated compound.
mass of dehydrate
4. Subtract the mass of the dehydrated compound from the mass of the hydrate to determine the mass of water that was present in the hydrate.
mass of water
5. Convert the mass of water to moles of water.
There are
moles of water. Because .3900g of H2O X 1 mol of H2O/18.0g of H2O= 0.0216 mol of H2O

6. Convert the mass of dehydrated compound to moles of the compound.
mol of CuSO4.(We know it is CUSO4 because the lab tolf us in the beginning) his is I used this calculation to come up with the mole amount 20.2120g of CuSO4 X 1 mol/159.608 g of CuSO4= 0.12663mol of CuSO4.
7. Divide by the lowest mole value to get a whole number mole ratio.
0.02160mol of H2O/0.02160=1
0.12663mol of CuSO4/0.02160=5.86250 (which is rounded to 6)
So every 1 CuS4 there are 6 hydrates. The formula would then be CuSO4*6H20.
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