In the exam, we covered all of the stoichiometry we've gone over this year so far. This includes converting moles to grams, finding mass given the mass of the reactants, balancing chemical equations, reaction particle diagrams, empirical formulas, and many other application of stoichiometry and the concept of Moles.
My overall score was an 83.3%. I scored 86.7% on the multiple choice, and 80% on the free response. Most of the questions I missed were not because of the lack of comprehension, however I feel I could have done better if I was more comfortable using the stoichiometry and molar mass tools that we learned in class or over the lectures. The hot potato quizzes helped with the test because they gave very similar questions.
Lewis Structures
Starting last Thursday, we were introduced to the Lewis Structure Diagram. This diagram is based on the atoms' outer valance electrons and their ability to bond with other atoms. The core charges of the atoms are equal to the number of dots in the diagrams. Shared electrons in a covalent bond are expressed with a line between the letters.
Some of the rules for Lewis Structures include:
1. The atom has to have the correct letter to represent the element and the correct number of valance electrons.
2. The sum of the shared electrons and the lone pair electrons must be eight--an octet.
3. Hydrogen is a duet.
The total number of valance electrons in a compound are the valance electrons of the individual elements added up.
F2=14 valance electrons
SiH4= 8 valance electrons
PCl3= 26 valance electrons
O2-2= 12 valance electrons
We did a Pogil ("Lewis Structure(1)")on this to make sure we understood the material. We also did some whiteboarding to compare our answers with other groups.
Main Ideas
Stoichiometry and the Lewis Structure do not connect in my head yet, because the Lewis Structure is still a new topic to us. However, the main idea of this week was to see if we understood stoichiometry (by taking the test) and becoming familiar with the Lewis Structure. I am relatively comfortable with the new material, so I do not have any questions. I feel that I participated a lot this week in our activities because (I think) I lead a lot of the discussions on the questions in the pogil in our group. My ideas changed about the Lewis Structure because I'm a little more comfortable with it, compared to last year.
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