Determining the Percentage of Water in a Hydrated Salt: A General Chemistry Lab Experiment, Assignments of Chemistry

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Percentage of Water in a Hydrant

General Chemistry I

Objective:

In this experiment we will be calculating the percent by mass of water in a hydrated salt, as well

as learning how to handle lab equipment without touching them.

Experimental:

1. Heat a crumble w/lid on a clay triangle for 10 minutes.

2. Then turn off flame and use crucible tongs to move it to a wire mesh to cool

3. Weigh the crucible

4. Add 0.75-1.0 grams of unknown hydrate to crucible and reweigh the crucible/lid/contents

5. Put the crucible with content back on flames for 10 minutes.

6. Cool crucible and weigh it.

Results and Discussions:

Table 1: shows the masses of measurements taken

Mass (g)

Mass of dry crucible 64.4116 g

Mass of wet powder 0.7745 g

Mass of dry crucible with wet powder 65.1861 g

Mass of dry crucible with dry powder 65.0223 g

Post-lab Calculations:

1. Mass of water lost = mass of crucible with wet powder - mass of crucible with dry powder ? = 65.1861 g - 65.0223 g Mass of water lost = 0.1638 g
2. Mass of sample = mass of crucible with wet powder - mass of dry crucible ? = 65.1861 g - 64.4116 g Mass of sample = 0.7745 g
3. Percentage of water = 𝑔𝐻^2 𝑂 𝑡𝑜𝑡𝑎𝑙 𝑤𝑒𝑡 𝑝𝑜𝑤𝑑𝑒𝑟 𝑥 100

In this lab, we were able to calculate the %H2O in the sample, and we were able to identify the unknown substance. Once we conducted the lab, we calculated the percentage of water to be 21.15% by using the formula, (Percentage of water = ). We also calculated the # of moles 𝑔𝐻^2 𝑂 𝑡𝑜𝑡𝑎𝑙 𝑤𝑒𝑡 𝑝𝑜𝑤𝑑𝑒𝑟 𝑥 100 presented in each element. Then, we finally figured out that our unknown substance to be Calcium sulfate dihydrate because the water percentage we calculated during the pre lab was very close to the experimental calculations.