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Home Q & A Board Science-Related Homework Help Chemistry (Moderator: Laser_3)
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michal.levy michal.levy
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11 years ago
The relative molecular mass of a hydrated salt is 246.The hydrated salt contains 51.2% of water. Calculate the relative molecular mass of the anhydrous salt and the number of molecules of water of crystallisation per molecule of the hydrated salt. (Answer: relative molecular mass of the anhydrous salt =120, Number of molecules of water of crystallisation =7) can someone write out the solution of that question?
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#1
11 years ago
If 51.2% is water then (100% - 51.2%) = 48.8% is not water.   48.8% of 246 = 120.

51.2% of 246 is 125.952 which represents some integral number of water molecules.  Divide  by the molecular mass of water:
125.952 / 18.0153 = 7 molecules of water
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