9.98 g of blue copper sulphate, CuSO₄ · 5H₂O (249.5 g/mol), is heated until it is white.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
of blue copper sulphate, (), is heated until it is white.
- What do you see?
- What mass of white powder () is left?
- What happens if a few drops of water are added to it?
Need a reminder? The key ideaShow
Water of crystallisation is the fixed number of water molecules in a crystal: , , . Gypsum heated to gives plaster of Paris, , which sets hard with water.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The blue crystals turn white, and drops of water form near the mouth of the tube.
Step 2. (b) , so .
Step 3. (c) It turns blue again and becomes warm.
Answer: (b) .
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