Copper (II) sulfate is a hydrated crystal with the formula CuSO4 . 5H2O and a deep blue color. When it is heated the crystals crumble and turn white. What would you do to restore the blue color?
Copper(ii) sulfate pentahydrate, CuSO4?H2O, loses the water of hydration when heated. The water molecules form an integral part of the crystalline structure, and when the water is removed, the structure is broken. All too often water is dropped back onto the white, anhydrous copper(II) sulfate erroneously thinking that the original structure is restored since the blue color returns. That simply isn't the case. When water is added back, some of the copper(II) sulfate dissolves in the water to make Cu2+ ions in solution. To restore the copper(II) sulfate to its original blue condition, the anhydrous copper sulfate must be dissolve in water and then recrystallized. That might take a week or two.
