Transcript
Gravimetric determination of water of hydration report
Known and unknown sample
Objectives:
The goal of this lab is to gravimetrically determine the water amount in a specific hydrate, and to learn how to write the formula of this hydrate.
Materials
Goggles
Laboratory notebook
Bunsen burner
Crucible
Hot hands
CuSO4
MgSO4
Analytical balance
Safety
Always ware goggles when working with Bunsen burner
Do not leave Bunsen burner without supervision
Keep papers/phones/ everything on the bench away from the Bunsen burner flame
Procedure
1- build up the stand that will hold the crucible over the Bunsen burner.
2- start the Bunsen burner, and place the crucible over it until the bottom turns red.
3-remove the crucible and let it cool on a glaze for 10mins
4-wiegh the crucible in the analytical balance to the 0.0001g and record, and then remove it
5-weigh 1 gram of CuSO4 of MgSO4
6-Transfer the sample to the crucible and reweight it, record to the 4th place
7-calculate. The mass of sample by subtracting the trade mass, and record.
8-heat crucible on low heat for 10 mins, gradually increase heat and wait for 10 mins
9-turn off heat, and let it cool for 10 mins and reweight.
10- repeat until you get a constant mass.
Data Sheet for known sample:
Data sheet for known sample:
Discussion:
In the experiment, we noticed that the height and hotness of the flame affects the final results. Because the aim of this experiment is to dry the hydrate and calculate the lost water, the heat plays a significant role, and adjusting the heat is crucial for the success of this experiment. The results achieved by heating the crucible multiple times and weighing them resulted in different data in the two labs. In the known lab, our experiment resulted in 5.5 moles of H2O for each mole of CuSO4. The accepted value of the ratio was 5, so the percent error is %10. I think what we did wrong was that we did not heat long enough to evaporate all the water in the sample. For the unknown sample, our result was 6 moles of water for every mole of MgSO4, And the accepted value was7. Therefore, the percent error is %14. At this lab, we used different analytical balance which could have been a systematic error. We also heated the sample a little more than 10 minutes, which led the sample to over dry. The results in this lab was achieved successfully. However, it could have been better if we 1- adjust heat properly 2-set an exact time for heating and cooling 3-wiegh in the same balance every time we weigh sample.
