Sodium sulfate decahydrate is used in chemical drying agent. how many waters are banned to sodium sulfate?

Explanation:

A hydrated compound is one that contains water molecules chemically bonded. So,  the correct question is how many waters are bonded to sodium suilfate?

The latin prefix deca means ten (10), and the word hydrate means that contains water; then, decahydrate is used in chemistry to designate a compound that is bonded to 10 parts (molecules) of water.

Hence, sodium sulfate decahydrate means that each molecule of the compound is bonded to 10 molecules of water.

In the chemical formula, the water molecules of a hydrated compound are shown after the chemical formula of the compound using a period and a coefficient (the number of water molecules bonded) before the water molecules.

Then, given that the chemical formula for sodium sulfate is Na₂SO₄, the chemical formula for sodium sulfate decahydrate is Na₂SO₄·10H₂O.