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Waters of Hydration

Waters of Hydration. Purpose:. Determine the formula of a hydrate from experimental data. Failure to wear EYE safety GOGGLES. Hydrate = chemical with water molecules loosely bonded to it. Anhydrous salt (removing water from a Hydrate) Waters of hydration.

preston-mitchell
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Waters of Hydration

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  1. Waters of Hydration

  2. Purpose: • Determine the formula of a hydrate from experimental data Failure to wear EYE safety GOGGLES

  3. Hydrate = chemical with water molecules loosely bonded to it. • Anhydrous salt (removing water from a Hydrate) • Waters of hydration Copper (II) Sulfate Pentahydrate CuSO4·5H2O

  4. Experimental Overview • Obtain mass of hydrate • Remove waters of hydration • Crucible dry • Obtain mass of anhydrous salt(hydrate with water removed)

  5. Remove waters of hydration – Heat to a constant mass • Heat sample (crucible) • Cool sample • Obtain mass of sample

  6. Remove waters of hydration – Crucible • Prepare crucible • Heat sample

  7. Prepare Crucible • Heat strongly for 5 minutes • Handle hot crucible with tongs. • DO NOT TOUCH with fingers. • Burns • Skin oils • Obtain combined mass of cool crucible

  8. Remove waters of hydration - crucible • Place ~2-3 grams of hydrate in crucible • Determine mass of hydrate, crucible Heat gentlyuntil no visible evidence of water remains • Color (sometimes) • “boiling” • Heat with blue flame ~5 minutes • When crystals turn white, heat additional 30 seconds then remove. • DO NOT overheat

  9. Dispensing solid reagents • ALWAYS replace the lid of a jar or bottle after dispensing a reagent. • Clean scoopula between dispensing substances. • Never return excess reagent to reagent jar.

  10. Use of the Balance • Sample cool for at least 10 minutes • Find mass again.

  11. Data AnalysisDetermine the formula of the hydrate • Determine the mass of the waters of hydration mass of waters of hydration = mass of hydrate – mass of anhydrous salt • Convert the mass of anhydrous salt to moles of anhydrous salt.  Moles of anhydrous salt = (mass of anhydrous salt)/(molar mass of anhydrous salt) • Convert the mass of the waters of hydration to moles of waters of hydration. Moles of waters of hydration = (mass of waters of hydration)/ (18.01 g/mole) • Determine the ratio of moles of water of hydration to moles of anhydrous salt. Moles of waters of hydration/moles of anhydrous salt Round ratio to an integer • Write the correct formula of the hydrate.

  12. 1. Mass of hydrated CuSO4•nH2O (Subtract crucible) 2. Mass of anhydrous CuSO4•nH2O (Subtract crucible) 3. Mass of nH2O (Subtract) 2.87g- 1.85 g = 1.02g 4. % of H2O in hydrate #3/#1 X 100 1.02g H2O/ 2.87g CuSO4•nH2O x 100 1. 2.87gCuSO4•nH2O 2. 1.85 g CuSO4 3. 1.02g H2O 4. 35.5%

  13. 5. Moles of H2O (1.02 g (1mol/18g H2O) 6. Moles of CuSO4 (1.85 g (1 mole/159.5CuSO4) Water units for each anhydride: 5. 0 .0567 mole H2O 6. .0116 mole CuSO4 4.89 = 5 0 .0567 mole H2O .0116 mole CuSO4 CuSO4•5H2O

  14. CuSO4•5H2O

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