1. Initial Dehydration:
* Anhydrous copper sulfate is a white powder.
* Upon heating, it absorbs water from the air, turning into hydrated copper sulfate (CuSO₄·5H₂O), which is blue.
2. Dehydration and Color Change:
* As you continue heating, the water molecules bound to the copper sulfate are driven off, leaving behind anhydrous copper sulfate again.
* This dehydration process causes the blue hydrated copper sulfate to turn white again.
3. Thermal Decomposition:
* If you heat the anhydrous copper sulfate even further, it undergoes thermal decomposition.
* The copper sulfate breaks down into copper(II) oxide (CuO), sulfur trioxide (SO₃), and oxygen gas (O₂).
* The reaction can be represented as:
```
2CuSO₄(s) → 2CuO(s) + 2SO₃(g) + O₂(g)
```
Key Observations:
* Color change: The color changes from blue to white and then back to white.
* Gas evolution: There will be a noticeable release of sulfur trioxide gas, which can be identified by its pungent odor.
* Residue: A black residue of copper(II) oxide remains after the decomposition.
Overall, the heating of anhydrous copper sulfate demonstrates the reversible nature of hydration and the thermal decomposition of a compound.
