CH301 Random Musings, October 14, 2009 1. The results from quiz 3 were spectacular near-80% average. Travis thinks he has fixed all the grading issues, so run check and see. By the way, I am very pleased with how this class is performing. Good for you. 2. Of course, I could be happier, like by not having students e-mail to complain about their in box being stuffed with junk mail that originates from my course e-mail lists, or complaints about students who do not respect the classroom learning environment. Please, show respect for your classmates when it comes to your use of electronic media and the seats you sit in. 3. Just in time to improve my mood, I received the following e-mail from a student who sat in my office last fall after failing my first test—not too differently than the nearly 90 of you who have made appointments. And this is what she said: Dr. Laude, I don't know if you remember me or not, but I took your chemistry class my freshman year, both semesters. I'm currently taking Organic with Dr. Iverson and we recently took our first test. I just wanted to write to you and tell you how much I appreciate your class and how you taught it even though it was really tough for me at first. On my first organic test I got a 92. I am so happy and I attribute a lot of my success to you. If you hadn't taken the time out to meet with me in your office and personally go over my study skills, I don't think I would have gotten the grade I got. I also appreciate you incorporating organic at the end of CH302. If almost killed my grade in your class, but I got through it and am now doing well in organic because of it. Thanks you so much again. So if you haven’t gotten in to see me, and even though it will be a few weeks before I have open times, do contact me. And if you haven’t heard back from an e-mail, try again. With so many e-mails some slip through the cracks. 4. There is a quiz coming a week from now and like clockwork one week early, here are the 6 question types on the next quiz 4. Also, a worksheet on gases this weekend, and two practice quizzes. • Determining bond order for a homonuclear diatomic molecule or ion (worksheet 7) • Determining paramagnetism for a homonuclear diatomic molecule or ion (worksheet 7) • Ranking bond energy or length based on bond order (worksheet 7) • Ideal gas law calculation for a chemical reaction involving gases (worksheet 8) • Ideal gas law calculation involving a state change in a gas system (worksheet 8) • Kinetic Molecular Theory explains gas speed, diffusion or effusion (worksheet 8)5. Definition corner: Here is some vocabulary to reinforce what you know as you put all the concepts about bonding together: • Electronic geometry refers to the shapes of the electron rich regions. So erase the atoms and just look at the electron pairs and the five possible answers. • Molecular geometry refers to the 13 possible shapes of the atoms in the molecule and ignores the electrons. So erase the electrons and just look at the shape the atoms take on. If you see a question that states: what is the shape of H2O, for example, they want to know the shape of the molecule and the answer is “angular” • Dipole moment: a vector describing the orientation of electron density. In this class the ΔEN is the dipole moment. • Ionic bond: ΔEN >1.5 Example: Na—Cl • Covalent bond: ΔEN <1.5 Example: C—O • Polar bond: ΔEN > 0 Example, Na—Cl or C—O • Non-polar bond: ΔEN = 0 Example, Br—Br or C—C • Polar molecule (asymmetry): ΣΔEN > 0 Example, H2O or CHCl3 • Non-polar molecule (symmetry): ΣΔEN = 0 Example, Br—Br or CCl4 • AOs are atomic orbits. Two AOs are need to make an MO and AOs are made from individual or combinations (hybrids) of s, p, d orbits • MOs are molecular orbits (which is a fancy way of saying bonds) and take an electron from two AOs to make either a s or p bond. • Resonance suggests that there are multiple identical Lewis structures that can be drawn when you have left over p bonds and too many locations on a molecule to put them. • Delocalization is what we should really call resonance. As the name suggests, left over p orbits tend to spread out (delocalize) over all the regions with identical Lewis structures. Every compound that has resonance actually has delocalized p electrons and so to sound like you know what you are saying, start inserting the word delocalized every time you want to say the word resonance. 6. Deep thought about bonds and molecules and why it makes your brain hurt: • Polar bonds can be either covalent or ionic, but non-polar bonds are always covalent • Non-polar molecules can be made of non-polar bonds (like Br2) but more commonly are made of polar bonds that cancel out to make a non-polar molecule (like CCl4 or BF3) • Ozone (O3) is crazy backwards. It contains multiple non-polar bonds between O and O, but because of that electron pair bending the bond angle around the central atom, it is a polar molecule!! Something to tell the folks at Thanksgiving. 7. Registration time for spring and summer classes is just around the corner. For those interested in taking my spring CH302 class taught at this time, you had your one, and likely only chance to get in by filling out a pink sheet on Tuesday. If you missed the sheet, and need to fill it in, let me know as soon as possible. 8. Public Service Announcements: Parent’s Day: Most of you are freshmen and too naïve to realize you don’t want your parents coming to visit on Parent’s Day. So good news, Parent’s Day is this weekend, on October 24th. Each of the Colleges puts on a nice event as part of Parent’s Day. In Natural Sciences we have an open house held from 9 to noon am on Saturday at the Texas Memorial Museum (the back of TMM is at the bottom of 24th and San Jacinto behind the mustang statue). There will be a brunch buffet, fun activities and the chance to meet faculty, look at some interesting research and program opportunities, and generally have your parent’s snoop into your college life (at least the academic part of it.) As I mentioned, if you bring you parents and introduce them to me, I will act like you have gotten to know me really well and that I think the world of you as a student and human being.9. Off by just a couple hundred degrees. When I get my cell phone wet I tend to bake it at 150
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