posted by Neha on .
Which of the following substances exist(s) as a resonance hybrid?
A. I only
B. II only
C. III only
D. I and II only
E. II and III only
Ans w/i 12 hrs please!!
I have answered two of these ASAP questions in which you want answers w/i a specified time; however, my answers have been complete w/o any work from you. You need to know that we try to HELP do homework; therefore, you should make an attempt at these questions, tell us what you think or why you are stumped. With this particular question, please post your thought as to the correct answer and why you think that. Someone will get back to you.
Well, I know that CO2 has resonance forms, but SO3 and HCO2 have resonance forms too. So that's why I don't get which one is the answer because all of them have resonance forms. I guess I just don't understand the "hybrid" part of the question, which would point to a right answer.
I think your problem may be that you didn't draw the Lewis structures. I found a CO2 structure and a SO3 one. For HCO2^- I looked up HCOOH. For that, just look at the Lewis structure and remove the H of the COOH group and you will have the HCOO^0 ion.
lewis structure CO2
lewis structure SO3
lewis structure HCOOH
The CO2 one is the one that has no resonance hybrids; i.e., that's about the only way you can draw CO2. However, for SO3 the double bond can move to ANY of the S-O bonds and for HCOOH the double bond can move to either of the C-O bonds. Therefore, SO3 and HCOO^- have more than one way of drawing them; hence, they have resonance forms.
But I thought that CO2 could be like O=C=O, O-C=-O, and O=-C-O. Thank you though, for your input. :) I'm sorry about just posting the questions again.
You are right. There are some that may argue that the :O:C:::O: and :O:::C:O: are contributors; however, it is clear from the choices you are given that these are not considered significant. The most logical reason is that the first one leaves a +1 charge on the left O and a -1 charge on the right O. The other form that is reversed of course. Whereas, the :O::C::O: leaves a zero charge on all three atoms which is far preferable. E is the best choice of those available.