The compound formula of hydrated sodium sulfate is Na₂SO₄·xH₂O, where 'x' represents the number of water molecules associated with each formula unit of sodium sulfate.

Here's why:

* Na₂SO₄ is the formula for sodium sulfate.

* ·xH₂O signifies the presence of water molecules in the crystal structure. The 'x' is a variable that indicates the number of water molecules per formula unit.

There are several different hydrates of sodium sulfate, each with a different value of 'x'. The most common ones are:

* Sodium sulfate decahydrate (Na₂SO₄·10H₂O) - This is the most common hydrate and contains 10 water molecules per formula unit.

* Sodium sulfate heptahydrate (Na₂SO₄·7H₂O) - This hydrate contains 7 water molecules per formula unit.

So, the specific formula depends on the particular hydrate.