"Anhydrous" itself is not a chemical compound and therefore doesn't have a chemical formula. It's a term that describes a substance that is devoid of water molecules.

To specify the chemical formula, you need to identify the specific compound that is anhydrous. For example:

* Anhydrous calcium chloride: CaCl₂

* Anhydrous sodium sulfate: Na₂SO₄

* Anhydrous copper sulfate: CuSO₄

So, the chemical formula for "anhydrous" depends on the specific substance being referred to.