Bile vitriol, also known as copper sulfate pentahydrate, has a chemical formula of CuSO4 5H2O.

You can also write: [copper (H2O) 4] H2SO4.

Under the condition of heating, the crystal water in the molecule will gradually lose;

[Copper (H2O) 4] H20-(△, about 100℃)→[ Copper (H2O) 2] H2O+2h2o

[Cu (H2O) 2] SO4 H2O-(△, about100℃) → [Cu] SO4 H2O+2h2o

[Cu] SO4 H2O-(△, about 258℃)→ CuSO4+H2O

If the purity of the sample is 100%, it can be determined that the reduced quality must be the quality of crystal water.

The amount of substance in the vitriol = 2.5g/250g/mol = 0.0 1 mol.

The amount of crystal water substance lost = (2.5g-2.14g)/18g/mol = 0.02mol.

According to the chemical formula, 0.0 1 mol of vitriol contains 0.05 mol of crystal water, which loses 0.02 mol after heating, leaving 0.03 mol.

It can be inferred that the chemical composition of the remaining solid is [Cu (H2O) 2] SO4 H2O or CuSO4 3H2O.