Composition stoich

Composition stoich - The CuSO 4 ·5H 2 O(249.7 g/mol will...

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Compound Stoichiometry - Mole Concept Consider a sample of copper(II) sulfate pentahydrate. It's a blue coarse crystalline substance and is sitting on a laboratory balance as shown below. The chemical formula for copper(II) sulfate is CuSO 4 ·5H 2 O. Note that the “·5” in front of the H 2 O means that 5 waters of hydration are part of the formula. The “·5” does NOT mean times fve ( ! 5). If the blue hydrated copper(II) sulfate is heated to 110˚C, 4 of the 5 hydrates (water molecules) will come off leaving only 1 hydrate. The formula for copper(II) sulfate monohydrate would be CuSO 4 ·H 2 O.and it is a very pale blue color. Note how there is only one hydrate left. It is “held” tighter than the other 4 hydrates and will not come off at 110˚C. However, if it is heated to 150˚C (or higher) the last hydrate comes off and you would then have anhydrous copper(II) sulfate which has a chemical formula of CuSO 4 and is white in color. Needless to say, the weights of equal amounts (moles) of each of these compounds will be different because of the waters of hydration.
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Unformatted text preview: The CuSO 4 ·5H 2 O (249.7 g/mol) will weigh the most and the CuSO 4 (159.6 g/mol) will weigh the least. Consider of all the different ways that a sample of 62.421 grams of CuSO 4 ·5H 2 O can be looked at by a chemist. Note that this is equivalent to 0.250 moles of CuSO 4 ·5H 2 O. 1.51 ! 10 23 1.51 ! 10 23 1.51 ! 10 24 1.35 ! 10 24 7.53 ! 10 23 1.51 ! 10 23 atoms of Cu atoms of S atoms of H atoms of O molecules of H 2 O formula units of CuSO 4 62.425 g 0.250 mol Cu 0.250 mol S 2.50 mol H 2.25 mol O 1.25 mol H 2 O 0.250 mol CuSO 4 15.888 g Cu 8.017 g S 2.52 g H 36.00 g O 22.52 g H 2 O 39.905 g CuSO 4 25.45% Cu 12.84% S 4.04% H 57.67% O 36.08% H 2 O 63.92% CuSO 4 100% 100% Note how the individual parts add up to make the whole: 15.888 + 8.017 + 2.52 + 36.00 = 62.425 g of Cu g of S g of H g of O g of CuSO4·5H2O Note also how you can view the sample in an elemental way (left of the green marker line), or simply as a compound (CuSO 4 ) and water (H 2 O) which is on the right side of the green marker line. © McCord 2006...
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This note was uploaded on 11/23/2010 for the course CH 10000 taught by Professor Mccord during the Spring '10 term at University of Texas.

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