Waters of a Hydration of a Salt Lab

Waters of a Hydration of a Salt Lab - is was that is just...

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Stephanie Warner Chem 153 Shidong Chu 7 October 2005 Waters of Hydration of a Salt Purpose: The purpose of this lab is to determine the moles of coordinated water driven off of the sample. Calculations: Run 1: Mass of H 2 O lost = W 1 – W 2 = 32.780 mg – 29.540mg = 3.240 mg 3.240mg x (1g / 1000 mg) = 0.00324 g H 2 O lost 0.00324 g H 2 O lost x (1 mole H 2 O / 18 g H 2 O) = 1.8 x 10 -4 moles H 2 O lost 0.02954 g unknown x (1 mole / 166.22 g unknown) = 1.78 x 10 -4 moles anhydrous salt Moles H 2 O lost/ moles anhydrous salt = 1.8 x 10 -4 / 1.78 x 10 -4 = 1.001 mol H 2 O/ mol salt Average: (1.011 + 0.9781)/2 = 0.99455 mol H 2 O/ mol salt Weight %: Run 1: (g H 2 O lost/ g sample) x 100 = (0.00324/ 0.03278) x 100 = 9.88% Average: (9.88 + 9.83)/2 = 9.86% average weight Questions: 1. Coordinated water is water that is bound to the molecules whereas absorbed water
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Unformatted text preview: is was that is just on the surface of the molecule. 2. Desiccants do not have enough affinity for water or capacity to dry “wet” samples. Desiccators are only used to store previously dried samples. 3. You can tell if your desiccant needs to be replaced if the desiccant is wet or saturated. This is because when the desiccant is saturated it can’t hold any more water; therefore it won’t be able to keep samples dry. 4. You don’t need to know the data collected during the middle of the TGA because you want to know the total amount of water being driven off. All you need to find this is the starting and ending masses....
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