[Ter]

Hi I have a problem here. I was wondering about Barium hydroxide hydrated crystals..how is it formed?

From my understanding, when a giant ionic lattice is dissolved in water, the cations and anions will act independently of one another and attract water molecules, the quantity of water molecules attracted will be based on their charge density.
At this point, I have one question, will a doubly charged anion attract more water molecules than a singly charged anion? Since a singly charged cation attracts lesser water molecules than a doubly charged cation but I am not sure for anions..

Continuing, since cations and anions behave independently of each other, these ions are excessively hydrated ( From what I know it means that an ion is surrounded by many water molecules) and thus crystalize out of solution to form hydrated crystals. However, how is it then possible to form barium hydroxide crystals? Barium hydroxide is a compound, consisting of a cation and an anion, how is it possible that they can come together? I thought hydrated crystals meant that it only consisted of an ion(either an anion or cation) and water of crystallization, that's all. What went wrong with my 'logic'?



Please help me out, I'd really appreciate it.
Thank you so much for your time

[fledarmus]

Simple ionic crystals can be thought of as a solid in which each cation is surrounded by anions and each anion is surrounded by cations. Depending on the size and charge densities of the ions, however, there may be enough open space within the crystal lattice that it can incorporate water molecules between the anion and cation in some positions.

There is a reasonable description, if rather old, of the actual structure of several barium hydroxide hydrate crystals to be found on page 190 of this report, in Appendix D - http://www.osti.gov/bridge/servlets/purl/5625798-n2qpwH/5625798.pdf