Select the compound that contains the carbon-oxygen bond that can be broken by photons of light with the longest wavelength.

asked by @chrisg38 • 10 months ago • Chemistry • 5 pts

A. Carbonate, CO32– B. Formate, CHO21– C. Carbon dioxide, CO2 D. Phosgene, CCl2O E. Formaldehyde, CH2O these are the choices, how would I solve this?

Add comment
1 answer

Hey there Chris! Looking at all the lewis structures, we see that we have 2 compounds that are able to resonate (electrons move around and form double bond with all the Oxygens. Even though resonance makes a molecule more stable, we need to take a look at their bond orders.

The bottom 3 compounds do not form double bonds with any other elements. CO2 already has 2 double bonds, so both of the O have a full double bond, or bond order of 2. Same for CCl2O and CH2O.

But for CO3^2- have a bond order of 1.33 because those 3 Oxygens all share the double bond, so the 3 Oxygens have 1/3 of the double bond, plus their single bond, Hence bond order of 1.33.

CHO2^-1 has a bond order of 1.5 because there is only 2 Oxygens sharing the double bond.

Now, we are looking for the C-O bond that will be easiest to break by a light with longest wavelength, which means the least amount of energy.

CO3^-2 has the smallest bond order, so those C-O bonds are the weakest.

Let us know if you have any further questions about this.

enter image description here

answered by @dashab2 • 10 months ago
  • Thank you! Chris commented 10 months ago