Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: FiendishFrog on September 13, 2007, 03:45:00 PM
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I seem to be stuck on this problem. I'm terrible at math. Could someone please help walk me through this so I can see how to do it? I have a feeling it is probably easier than I am making it out to be. Many thanks.
The solubility of phthalic acid in water is: 0.54g/100 mL at 14°C, 18g/100 mL at 100°C.
How many mL of boiling water are required to dissolve 175.0 g of phthalic acid?(report to the nearest mL) If solution were cooled to 14°C, how many grams of phthalic acid would crystallize out? (report to one decimal place)
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175.0 g to be dissolved in 100oC water with solubility 18g/100 ml.
straightforward, no?
then you have a volume V in which 175g is dissolved. you cool that down to 14oC with solubility 0.54g/100ml. So you get a new figure of mass of phtalic acid that can maximally be dissolved in volume V at 14C.
the difference between the initial 175g and the new mass will crystallize out.
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So would I do something like this? -->
175g * (100 mL)/18g = 972 mL boiling water
972 mL * (.54 g/ 100 mL) = 5.25
175- 5.25= 169.75
I'm still not sure I completely understand. I find it very difficult to keep everything straight.
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Looks OK :)