In the chemical formula CaSO₄·1/2H₂O, only half a water molecule is shown because two formula units of CaSO₄ share one molecule of water during the formation of calcium sulfate hemihydrate.
Why is only half a water molecule shown in the chemical formula of calcium sulfate hemihydrate?
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The chemical formula for calcium sulfate hemihydrate, CaSO₄·0.5H₂O, indicates the presence of only half a water molecule. This is because hemihydrate means “half hydrate.” In the process of forming calcium sulfate hemihydrate, one water molecule is released, leading to the representation of half a water molecule in the formula. The dot in the formula indicates the water content, and the coefficient “0.5” signifies that only half of a water molecule is associated with each unit of calcium sulfate hemihydrate, reflecting the specific stoichiometry of the compound.