Question

The greenhouse effect is caused by gases in the atmosphere that trap heat. We know that the atmosphere is made up of 21% O₂ and 78% N₂. The other 1% consists of traces of CO₂, NO₂, CO, NO, O₃, N₂O, CH₄, and CFC’s like CFCl₃, CCl₂F₂, and CCl₃CHF₂.

A) Draw the Lewis structure of N₂, NO₂, and CFCl₃. Indicate the total number of valence electrons in each structure. Submit a photo of your drawing with your ID card.

N₂                                                                   NO₂                                                    CFCl₃

total e-s = _____                                   total e-s = _____                           total e-s = _____

B) Indicate the types of bond(nonpolar covalent/ polar covalent.) present in each of these compounds? Explain your answer

C) Draw another resonance structure for NO₂ and label each bond as sigma or pi, Submit a photo of your drawing with your ID card.

D) Deduce the hybridization for the central atom in CFCl₃ and NO₂. Explain how you arrived at your answer.

CFCl₃                                                                                                                        NO₂

E) Using VSEPR, predict the molecular geometry for each below, indicating the bond angles in each molecule. Explain why the molecule adopts that geometry.

N₂                                                                   NO₂                                                    CFCl₃

F) A greenhouse gas is only a greenhouse gas if 1) it has a dipole moment or 2) can be bent or distorted to have a dipole moment. This enables it to absorb heat and emit it back to the earth’s surface, hence trapping the energy as heat. Redraw the Lewis structure of each molecule below showing its correct geometry. Indicate the direction of the bond dipole for each bond in blue. Then, show the direction of the resultant dipole moment in red, if any. Submit a photo of your drawing with your ID card.

N₂                                                                   NO₂                                                    CFCl₃

G) Go to the following website to view a simulation of how some of these molecules interacts with infrared radiation.(https://phet.colorado.edu/en/simulation/molecules-and-light). Based upon your work in f) and what you learned from the simulation, which molecules should be greenhouse gases? Explain.

Answer 1

For the green house gases

A) drawn below are lewis diagrams

B) N2 is non-polar

NO2 is polar

CFCl3 is polar

C) Resonance structure for NO2 is below

In N-O : it is sigma bond between N and O

In N=O : we have one sigma and one pi-bond between N and O

D) Hybridization

C attached to four bonds : sp3

N atached to two oxygen atoms : sp2

E) N2 : linear (180 o bond angle) as N N forms triple bond

NO2 : trigonal pyramid as lone pair of oxygen and extra electron does not let molecule in linear shape.

CFCl3 : tetrahderal and 109 0o bond angle as expected for tetrahedral molecules.

F) The direction of dipole in each case is towards the more electronegative atom. Shown below are structures.