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Hydrates

“A solid compound containing water molecules combined in a definite ratio as an integral part of the crystal”. Hydrates. What is a Hydrate?. Any salt that has water chemically bonded to the ions in the crystal structure is a hydrate or hydrated crystal. Copper(II) sulfate is a hydrate.

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Hydrates

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  1. “A solid compound containing water molecules combined in a definite ratio as an integral part of the crystal” Hydrates

  2. What is a Hydrate? • Any salt that has water chemically bonded to the ions in the crystal structure is a hydrate or hydrated crystal. • Copper(II) sulfate is a hydrate. • Hydrated copper(II) sulfate is deep blue in color.

  3. What does the Chemical Formula of A Hydrate Look Like? • BaCl2•2H2O • FeSO4•6H2O • Na2CO3•10H2O • CuSO4•5H2O

  4. How are Names of Hydrates Written? • BaCl2•2H2O • FeSO4•6H2O • Na2CO3•10H2O • CuSO4•5H2O • BaCl2•2H2O • barium chloride dihydrate • FeSO4•6H2O • iron(II) sulfate hexahydrate • Na2CO3•10H2O • sodium carbonate decahydrate • CuSO4•5H2O • copper(II) sulfate pentahydrate

  5. What prefixes are used?

  6. Practice Naming • http://www.chem.purdue.edu/gchelp/nomenclature/hydrates_2009.htm

  7. How can the water be removed? • Heat the crystal. The water is loosely bound, and will come away as water vapor. • Put the crystal in contact with or near a desiccant, maybe in a desiccator.

  8. What is the compound called after the water has been removed? • Anhydride (noun) • The light blue powder is the anhydride. • Anhydrous (adjective) • Anhydrous copper(II) sulfate is left in the test tube after heating.

  9. How is a hydrate formed? • A substance that absorbs water from the air is said to be hygroscopic.

  10. How to find the formula of a Hydrate • To determine the water content of an ionic hydrate sample, we measure the mass of the sample before and after heating. • Based on the analysis, we can express the water content of the hydrate

  11. Finding Formula of a hydrate • calculate the mass % of water in the hydrate. • mass of water in the hydrate sample equals the mass lost upon heating. • Based on the mass of water and total sample mass, we can calculate the mass percent of water

  12. Mass percent of water, % = (mass of water/ mass of original sample) x 100

  13. Determine number of moles • Mass of anyhdrous portion = mass of substance left after heating • Figure out how many moles there are of water and of anhydrous portion • Divide number of moles of water by the number of moles of anhydrous portion – this gives you the number of moles of hydration

  14. Finding Moles of Water of Hydration • Number of moles of waters of hydration = moles of water/ moles of anhydrous compound

  15. Writing the formula • Once we have determined the number of moles of the water of hydration, we can write the chemical formula for the anhydrous compound, followed by a raised dot, followed by the number of waters of hydration obtained by calculation.

  16. Example hydrate problem Let’s make things a little more clear

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