Hydrate Water Percentage Calculator

1. Find the molar mass of the water of hydration (number of water molecules × molar mass of H₂O).
2. Find the molar mass of the anhydrous compound + water (total molar mass of the hydrate).
3. Calculate the percentage of water:

Percentage of water=mass of watermass of hydrate×100%\text{Percentage of water} = \frac{\text{mass of water}}{\text{mass of hydrate}} \times 100\%Percentage of water=mass of hydratemass of water​×100%

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Step-by-step example:

If you give me the formula of the hydrate, for example:

• CuSO₄·5H₂O (Copper(II) sulfate pentahydrate)

Then:

• Molar mass of CuSO₄ = (Cu)63.55 + (S)32.07 + 4×(O)16.00 = 63.55 + 32.07 + 64.00 = 159.62 g/mol
• Molar mass of 5H₂O = 5 × (2×1.01 + 16.00) = 5 × 18.02 = 90.10 g/mol
• Molar mass of hydrate = 159.62 + 90.10 = 249.72 g/mol

Water % = (90.10 / 249.72) × 100 = 36.08%