Easy Chemistry assignment
1 – Piece of cake – under “spring break labs” find
a) a photograph of the result of adding two solutions of electrolytes together. The experiment itself consists of a pictorial array of these reactions. For each combination of ions – tell whether the observed reaction fits the predictions found in the various tables and charts.
For instance: Na+ and OH-. No reaction is observed. The solubility rules indicates that all sodium compounds are soluble and the most chlorides are soluble except for silver, mercury and lead chlorides. So the in chart provided – you would put “follows rules” or something else that effect that indicates that the general rules work. There will be exceptions!
b) Using electronic structure programs. Follow the example given for the hydrogen molecule.
The purpose of the lab is twofold.
1. Prove to yourself that the “cubes and balloons” rules actually work most of the time – the shape and number of bonds are correct.
2. Show that the periodic trends for electronegativity also work – most results from WEBMO include some description of partial charge. In carbon dioxide, the carbon should be slightly positive and the oxygens slightly negative. The bond length should be shorter that the usual C-O single bond and the molecule should be linear!. Guess what! “cubes and balloons do work!”
The computational programs will allow you to see things that I have been waving my hand over. When you solve for :MO’s or Molecular Orbitals, you will see orbitals listed with negative energies of interaction. Negative is good – it means attractive, lower energy states. The program will give you a list of them as well as their probability distributions. You will also see “antibonding orbitals” with positive energies of interaction. These are those “excited states” that we talk about when we draw our two level (ground and excited) energy diagram.
Now you can visualize them, For the hydrogen molecule (H2) we expect the ground state electrons to occupy space between the two atoms. Where would electrons in “exited states or antibonding orbitals” go? Take a look!
