## Chemistry Students: Remember the Water of Crystallization

[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…

## Calculate Atom Weight Two Ways

[caption id="attachment_8437" align="alignright" width="400"] Radon atom statistics.[/caption] Ever wonder how much an atom weighs? One atom. Different varieties of atoms weigh different amounts—helium weighs one thing, lead another. But how can the weight of any sort of atom be determined to within reasonable accuracy? We present two simple methods to calculate atom weight. Two Ways One can calculate atom weight from knowing the weights of the constituent electrons, protons, and neutrons. If you know the weight of each of those and the number of each in an atom, you can readily calculate its weight. Yet, there is an easier and a better way. Let’s pick an element out of the hat. Let’s take gold (If we can’t afford it, at least we can talk about it.). To calculate atom weight…

## Which Weighs More – Wet Air or Dry Air?

[caption id="attachment_5407" align="alignright" width="440"] CCA Share Alike 3.0 Unported by Santhosh kumar[/caption] Air is mostly a mixture of gases and plus water vapor. The primary two gases are nitrogen and oxygen. We will state up front that the traces of other substances in air don’t affect the outcome of whether wet air or dry air is heavier. It all has to do with molecular weights. Nitrogen Nitrogen is a diatomic gas—chemical formula N₂. Its atomic weight is 14, therefore its molecular weight is 28. Nitrogen constitutes 78% of the atmosphere. [caption id="attachment_14807" align="alignright" width="280"] Barometer[/caption] Oxygen Oxygen is also a diatomic gas—chemical formula O₂. Its atomic weight is 16, therefore its molecular weight is 32. Oxygen constitutes 21% of the atmosphere. Dry Air Again, not considering the traces of other…