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💧Hydrate vs Anhydrous🏜️

Many salts can hold water within their crystals. Whether water is present makes a compound a hydrate or anhydrous.

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💧Hydrate
  • Contains water within the crystal lattice
  • Has a fixed water-to-formula ratio
  • Written with a dot, like CuSO4·5H2O
  • Often more colorful, like blue copper sulfate
  • Loses water when heated
🏜️Anhydrous
  • Contains no water of crystallization
  • Formed by heating a hydrate
  • Often a different color from the hydrate
  • Can absorb water and become a hydrate again
  • Example: white anhydrous copper sulfate

Verdict

A hydrate carries a fixed amount of water locked in its crystals, while an anhydrous compound has none. Heating drives water off; exposure to moisture can bring it back.

Frequently asked

How do I make an anhydrous compound?+

Heat the hydrate to drive off the water of crystallization.

Why does copper sulfate change color?+

Hydrated copper sulfate is blue, while the anhydrous form is white.

Is the water amount fixed in a hydrate?+

Yes. Each hydrate has a definite ratio of water molecules per formula unit.

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