For students taking Chemistry 101 at the University of Victoria in the Fall 2013 term.
No question, just wanted to comment on the unicorn/dragon/rhinoceros explanation of resonance structures. I thought it illustrated the concept really well and I'm definitely going to remember it because it was kind of unusual. Thanks!
I was wondering if some one could post the answers to the multiple choice of the sample mid term F02 was assigned. I am not in the class but I would like the answers to check my work.
anyone knows when is the midterm results going to be published? and how did everyone find it?
I have asked around and no one seems to know when the midterm marks are oging to be posted. Umm i thought the multiple choice wasn't bad.... but the written was a bit challenging. But guess we will have to wait and see!:)
Do we need to know anything regarding oxidation numbers? It came up a couple of times in the textbook study questions, but I don't recall it being mentioned in the lectures.
There are some questions on the practice exam regarding isomers and i was just wondering if we can expect similar problems on the midterm or final?
No, there is no organic chemistry in the midterm.
Hey Dr. McIndoe..if we have a molecule such as NO2^+, which has three possible Lewis structures, are these structures resonance even though one of them doesn't have as good formal charge distributions as the other two? ie. must the three structures be equally important for them to be in resonance? haha I hope I'm making some sense....
Er, not completely, but I'll have a stab at explaining what I think you're asking. "Resonance" is a lousy word - I wish textbooks just used "delocalisation" but we're stuck with the "R" word now, even though nothing is actually resonating or in resonance. Different plausible Lewis structures (the unicorn, the dragon) help us recognise the possibility of delocalisation, but they don't have to contribute equally to our picture of the molecule (the rhinoceros). A good example is NCO-; the major contributor is the N(triplebond)C-O, where the -ve charge is on the electronegative O. Less important is N=C=O, where the -ve charge is on the N, and practically insignificant is the N-C(triplebond)O, which puts a double -ve charge on the N and a positive charge on O. So weighting these different structures appropriately to get our actual structure, we'd expect most of the negative charge to be on O (but some on N), and a CN bond order of more than 2 and a CO bond order of less than 2. Hope this helps.
yep that's perfect thanks for the help!...and the class.
Post a Comment