First, before the worksheet, we went through some Lecture Quizzes that gave us an understanding of how to draw Lewis Structure Diagrams. Here are the steps:
1. Calculate the total number of valance electrons for the molecule.
2. Draw the skeleton structure for the molecule. The least electronegative element should be the central atom.
3. Make bonds between the surrounding atoms and the central atom.
4. Distribute as many remaining valence electrons to the surrounding atoms until their octet (or duet) are filled.
5. Distribute the rest to the central atom. If there is not enough, borrow lone pairs of electrons from one or more surrounding atoms and create multiple bonds until the Octet Rule is satisfied.
This week, we started off with a Pogil on Bond Order and Bond Strength. Bond Order is the number or pairs of electrons that are shared between two elements. Bond Energy (kJ/mole) is the energy required to sever the bond that holds two adjacent atoms together in a molecule. We found that the bigger the bond order, the bigger the bond energy. Bond length is the distance between the nuclei of two bonding atoms. As bond length increases, bond energy decreases.
We went through lots of practice to become comfortable with this material. I feel that I understood this pretty well, because it is basically a little bit more detail added to the Lewis Structure Diagram.
Brass Lab
Before we started our lab, we received a sheet of productive and non-productive beginning questions.
This week, we started on our Brass lab. The main goal of this lab is to find the percentage by mass (mass percent) of copper in brass screws. As a class, we decided to investigate these question: what is the relationship between the absorbance of the solution and the concentration of copper, and how does deducting concentration visually compare to the measurements of the colorimeter?
The procedure includes reacting the brass solution in HNO3 to produce a light blue solution of Copper.
Then, we took the stock solution of 0.393M and made a serial dilution of 0.200M, 0.100M, 0.050M, and 0.025M. We then measured the absorbance using the colorimeter.
Next week, we will interpret the class data and write our lab report.
VSEPR Theory Lab
We were introduced to the VSEPR Theory on Friday. VSEPR Theory predicts the shape an individual molecule will take depending on their bonding and non-bonding electron pairs.
Electron domains are the number of bonds there are between the elements. For example, carbon dioxide has an electron domain of two, because there is one bond between O and C, and another between C and O.
The shapes of the pairs are not perfect circles or lines. To show this, we tied small red balloons to represent the bonded pairs and larger white balloons to represent the non-bonding pairs. For example, ClF3 would look like this:
To go along with the new material, we did VSEPR Theory Lab (I), as well as the balloon models.
Main Ideas
This week, I feel like we went deeper into the bonds that tie together the elements and the structure of the molecules. However, I still have trouble understanding the shape of the compounds according the the VSEPR theory. The balloon structures representing the region in which the electrons are most likely found make sense to me, but I don't understand how the actual molecules look like. I think I will come to an understanding once we go over this worksheet and see the other models of other molecules. Other than that, I feel I understand the material we went over this week. I think there will be more problems when we enter the next week, where we discuss the results of the Brass Lab and finish up the VSEPR theory lab. Because I was not in class on Tuesday, I don't think I've participated very well this week. My ideas about the structure of a molecule has definitely changed after the VSEPR theory lab. I also feel really excited about doing more labs in this class now that we did a lab with real chemicals and fairly strict safety precautions. I just need to remember to use more drawings in the lab procedures.
No comments:
Post a Comment