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Topic: amount (in kg) to be dissolved in a saturated solution?  (Read 2980 times)

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Offline ichidp

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amount (in kg) to be dissolved in a saturated solution?
« on: September 08, 2012, 02:59:44 AM »
the problem is:

How much CaCl2 6H2O must dissolved in 100 kg of water at 20° C to form a saturated solution? The solubility of CaCl2 at 20° C is 6.7 gmol anhydrous salt (CaCl2) per 100 kg water.

what i did was took the kg of CaCl2 6H20 from the (MW CaCl2 6H20)/(MW CaCl2) ratio multiplied by 100kg water multiplied by the given solubility which i converted to (kg CaCl2/kg water).

the answer i got was 148.598 kg CaCl2 6H2O. however, the answer according to the answer key was 535 kg. i don't understand why. any help is very much appreciated, thank you! :)
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Offline Borek

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Re: amount (in kg) to be dissolved in a saturated solution?
« Reply #1 on: September 08, 2012, 03:29:33 AM »
Seems to me like you forgot you are changing amount of solvent.
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Offline ichidp

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Re: amount (in kg) to be dissolved in a saturated solution?
« Reply #2 on: September 08, 2012, 03:37:14 AM »
solvent? i thought, the solvent was given as 100kg, so why would it change?
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Offline Borek

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Re: amount (in kg) to be dissolved in a saturated solution?
« Reply #3 on: September 08, 2012, 03:42:09 AM »
CaCl2·6H2O
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Offline ichidp

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Re: amount (in kg) to be dissolved in a saturated solution?
« Reply #4 on: September 08, 2012, 04:26:51 AM »
wow. i think i finally got it, well, close to 535, i got 531 kg.. thanks!

i actually gave the wrong given up there, the solubility is supposed to be  6.7 gmol anhydrous salt (CaCl2) per kg water.
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