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what does it mean by hydrated

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hydrowire:
I have a compound and it says it is hydrated, waht does hydrated means anyway?

e.g. hydrated ethanedioic acid, H2C2O4.2H2O

does this solution forms ions? how does the water molecule relates to the ethanedioic molecule?

Borek:
Solid forms crystals. In crystal lattice there are molecules of water per every molecule of substance. That's what hydrated means in case of oxalic acid.

Once the substance is dissolved every ion is surrounded by water molecules, but not in stoichiometric ratio. This is called hydration too (unless my English fails here).

Try wikipedia on hydrates.

hydrowire:
Why we need hydrated oxalic acids? whats the difference between non hydrated(is it called anhydrous?) oxalic acids and hydrated oxalic acids?

Dude:
Hydrated in this case means that a somewhat stable amount of water is adsorbed by the salt.  If you were to make a 1 M solution of oxalic acid, the 2 moles of water are INCLUDED as part of the molar mass.  Thus, you would need more of a hydrated oxalic acid salt to attain a 1 M solution than an anhydrous oxalic acid salt since a portion of the molar mass is water.

hydrowire:
So what does this sentence means: To determine the mass of sodium ethanedioate(oxalate) used to prepare a solution containing sodium ethanedioate(oxalate) and hydrated ethanedioic(oxalic) acid.

how can it forms hydrated oxalic acid? by adding water with the right amount?

Is it correct that,
Sodium Oxalate - aqueous solution?
hydrated oxalic acid - solid crystal?


thx in advance.

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