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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: rhiannon on July 07, 2004, 06:59:56 PM

Title: hydrated formulas
Post by: rhiannon on July 07, 2004, 06:59:56 PM

i need to determine the concentration of a specific element
of a hydrated compound in solution in ppm, do i need to
include the water in the molecular weight?

Title: Re:hydrated formulas
Post by: Donaldson Tan on July 07, 2004, 09:25:07 PM

Upon dissolution, the water of crystallisation belongs to the solution. It's no longer part of the salt. You need not include water of crystallisation in the ionic formula mass of the salt for calculation of ppm. But in order to contribute to accuracy, you could add the tiny amount of water from the hydrated salt into the water solvent.

Title: Re:hydrated formulas
Post by: rhiannon on July 08, 2004, 02:01:34 PM

i think i may have worded my question wrong.
say i have 5 mg CaCl2(dot)6H2O and i need to
find the concentration of Cl in solution, if i get
the mass percent of Cl from the formula can i
still leave the weight of the water out?

Title: Re:hydrated formulas
Post by: Mitch on July 08, 2004, 04:46:35 PM

You still have to include the water.