Chemistry Students: Remember the Water of Crystallization

Chemistry, Education
[caption id="attachment_24966" align="alignright" width="480"] Don't forget the water.[/caption] Chemicals are, for the most part, categorized into inorganic compounds and organic compounds. The expression "water of crystallization" is rarely applied to organic compounds, since most of them are not water soluble, and if they are, few even of those form crystals with water. What IS Water of Crystallization? A high percentage of water-soluble inorganic salts form crystals that include water in their crystal lattice. An example of a salt, with and without water of crystallization is cupric sulfate.1 Such salts, deprived of water content, are termed anhydrous. In our example, we might speak of copper sulfate anhydrous.2 Quantity of Water [caption id="attachment_24967" align="alignright" width="380"] Fine crystals of copper sulfate pentahydrate.[/caption] Hydrated copper sulfate includes 5 molecules of water in its crystalline…
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The Molecular Structure of Hydronium Ion Hydrate

Chemistry, Physics
[caption id="attachment_16126" align="alignright" width="440"] Simple hydronium ion, unhydrated.[/caption] Abstract: The water molecule, H2O, can attach a hydrogen ion (H+) perhaps from a dissolved acid, to become a hydronium ion, H3O+, sometimes called a hydroxonium ion. This ion, if surrounded by water molecules, can form additional hydrogen bonds with them as well. The question is what is the molecular structure of the resulting hydronium ion hydrate? The mind conceives two serious possibilities. But what do studies reveal? Background It is a general principle of nature that a system is more stable if charges are spread out as much as possible. In the field of chemistry, the best known example of this involves water. Although the sum total of the electric charge of a neutral water molecule is zero, as the image…
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Instant Pudding Thickening Chemistry

Chemistry, Food
Ordinary “cook” pudding, such as Royal Pudding or Jello Pudding, has been around for decades. It is a starch product that, combined with milk, sets into semi-solid form through heating. However, “instant” pudding utilizes a different thickening mechanism. In fact, two thickening mechanisms. What are the mechanisms for instant pudding thickening? A Concrete Thickening Model It’s like making concrete from Portland cement! Really, like that? Think of what the Portland cement contains. It is largely a mixture of silicates. Among these are dicalcium silicate (CaO2)2•(SiO2) and tricalcium silicate (CaO2)3•(SiO₂2). Mixing the cement powder with water yields an inorganic polymer matrix. We will introduce a model for the thickening process of instant pudding in just a moment. First, though, you may enjoy looking at this very early Jell-o Instant Pudding commercial…
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Anhydrides – Inorganic and Organic

Anhydrides are compounds that are similar to other compounds from which one or more molecules of water has been eliminated. An anhydride must not be confused with an anhydrous compound. In an anhydrous compound, the water reactant from which it is formed includes water that is attached lightly by weak bonds. Water is not an inherent part of the molecule's structure. Consider cupric sulfate pentahydrate, CuSO₄•5H₂O. This is a blue, crystalline substance. It is a composite structure of one molecule of cupric sulfate and five weakly held molecules of water of crystallization. Those water molecules can be removed quite easily. Powdering the crystals and warming them in a drying oven produces CuSO₄. This anhydrous compound is nearly white. No, it is not an anhydride. Aluminum Oxide Aluminum oxide, Al₂O₃, is an…
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