Using the mole to work out the formula Activity
In the blue crystal structure of hydrated(containing water)copper sulfate there is a certain number of water molecules attached to each unit of copper sulfate. Our task is to find how many water molecules per copper sulfate units exist in our sample of blue(hydrated) copper sulfate.

Step 1 -weigh the crucible

Step 1 Weigh the empty crucible.
Record the weight - 35.03 grams


Step 2 Weigh the crucible and copper sulfate.

Record the weight - 64.10 grams

Step 2 -weigh the crucible  and sample of hydrated copper sulfate.(64.10grams)
Step 3 -heat the copper sulfate until it turns grey in colour.

Step 3 Heat the copper sulfate to drive off the water.


Step 4 Once the copper sulfate has turned grey take it off the flame and allow it to cool. Weigh the sample.

Step 5 Place it back on the flame and continue to heat for 5 more minutes. Reweigh the sample and repeat step 5 until the sample does not decrease in mass any further.

Step 4 -allow the copper sulfate to cool and weigh.\
Step 6 weigh the sample and record the final mass of the sample and crucible. (51.87 grams)

Step 6 Weigh the final sample .

Record the weight - 51.87 grams


Is water responsible for the blue colour of the crystal? View the video on the right

What is released as water is added?

Continue with the calculations