Here's what happens when these compounds are heated strongly:
FeSO₄·7H₂O (Iron(II) sulfate heptahydrate)
* Dehydration: Upon heating, the heptahydrate loses its water of crystallization. The following reaction occurs:
FeSO₄·7H₂O(s) → FeSO₄(s) + 7H₂O(g)
* Decomposition: Further heating of the anhydrous FeSO₄ leads to its decomposition:
2FeSO₄(s) → Fe₂O₃(s) + SO₂(g) + SO₃(g)
* Observations: You'll observe the following:
* The blue-green crystals of FeSO₄·7H₂O will turn white as the water evaporates.
* The white solid will further decompose, turning brown as Fe₂O₃ (iron(III) oxide) forms.
* You will smell sulfur dioxide (SO₂) gas, which has a pungent odor.
FeSO₄ (Anhydrous iron(II) sulfate)
* Decomposition: Anhydrous FeSO₄ decomposes directly upon strong heating, following the same reaction as above:
2FeSO₄(s) → Fe₂O₃(s) + SO₂(g) + SO₃(g)
* Observations:
* The white solid will turn brown as Fe₂O₃ forms.
* You will smell sulfur dioxide (SO₂) gas.
Important Note: The exact temperature at which these reactions occur and the specific products formed can vary slightly depending on the heating conditions.
