9/23-9/27

This week was pretty slow in AP Chem. We spent the first half of the week reviewing and taking our test on stoichiometry. The test covered limiting reactants, empirical formulas, and percent yield. I thought that the test was a good challenge and a good measuring stick for myself. I know I am capable of doing better, I just have to study more and do more practice problems before the test. For the rest of the time this week we went over Lewis structures.

            So far, I have found the material that we have gone over on Lewis structures fairly comprehensible. The main ideas that we covered on Lewis structures were how to figure out which atom is the central atom and how to form the covalent bonds. To figure out which atom is the inside atom, you must determine the electronegativities of the atoms. Then, you find out which atom has the lowest electronegativity and place it in the center. Then you form covalent bonds with unpaired electrons from the outside atoms to the inside atoms. We didn’t really go over this in class but resonance and bond order was discussed in the lectures. I found these two concepts a bit more confusing but I’m hoping we work on them in class so I can gain a better understanding.

            Overall, this week was pretty light so there isn’t too much to discuss here. I found the activities that we did to gain knowledge on Lewis structures pretty straightforward and the lectures on resonance and bonding orders a bit more complex. I learned from taking the test this week that I need to work harder on doing more practice problems and studying harder to get a higher grade on the test. I would still rate my understanding on the past material covered on the test and the new material that we learned this week at about a 4 out of 5. I was able to participate fully in all of the activities we did this week and that helped me broaden my thinking about Lewis structures and how they really work.

How to draw Lewis dot structures: http://www.youtube.com/watch?v=z3F7LjTvdX0

Week of 9/16-9/20

            This week we learned more about stoichiometry, in particular limiting reactants, yield, and empirical and molecular formulas. We have been working since the start of the year on stoich problems and this week we further advanced our knowledge on the subject. The further we go into the matters of stoich, the more they build on each other. Our knowledge that we developed in the first couple weeks on molar masses and the mole ratio has been crucial to helping us do problems with limiting reactants, yield, and empirical and molecular formulas.

            We developed our knowledge on limiting reactants through a pogil that we completed. This was very helpful and gave me a better idea on what was really going on when we did problems involving finding the limiting reactants. From there we did some more worksheets to get more practice with finding the limiting reactants. To find the limiting reactant you must find out which of the reactants produces the lesser amount of product. To figure this out we use our knowledge on mole ratios and molar mass to perform calculations. I found these problems fairly simple and straightforward.

            Next we worked on finding the percent yield of a product. We used the lectures and worksheets to understand what was really happening when you look for the percent yield of a product. To solve yield problems you must: balance the equation, determine the limiting reactant, determine theoretical yield, divide the actual yield by theoretical yield and multiply by 100 %. This process is pretty simple and doesn’t involve that hard of math. I thought that I was able to understand and complete all of the problems involving yield fairly easily. I don’t have any questions about percent yield of products because I get the idea to its full extent.

            The last thing that we worked on this week was determining empirical formulas. Like limiting reactants, we discovered empirical formulas through a pogil. At first the idea of empirical formulas didn’t make too much sense but once we were through the pogil the concept was much clearer. By doing the pogil, it was determined that an empirical formula is a formula that represents the simplest ratio among the elements of a compound. However, that doesn’t mean that formulas with the same base formula don’t exist. We found this out when we did a worksheet that had us find the molecular formula by dividing the molecular molar mass by the empirical molar mass. I thought this equation was simple and easy to understand and I had no problem with this worksheet. We also dabbled a little bit in drawing particle diagrams. I was a little bit more confused by this and I was hoping we would work on it more in class.

            All in all, I thought this week I was able to comprehend all of the material and my participation was very high. On a scale of 1-5, I would say I’m at a 5 on the ideas we learned this week. I still need to work a little more on particle diagrams but I think that’s about it. I have to think more about how this process works and how we balance equations with particle diagrams.

Week of 9/9-9/13

            This past week we performed a lab looking at the relationship between concentration and absorbency. We also took a look at molarity and worked with a few stoich problems. These were the main ideas that we covered this week and they are very much related to each other. The main concept that connects everything we did this week is concentration is related to molarity and we used this knowledge to assist us in our lab.

            The first activity that we did was complete a lecture quiz on molarity. What we learned from this lecture quiz is the equation: Molarity (M)= moles of solute/volume of solution in liters. This concept is very important to understand and connects with the idea of dilution that we saw in the lab. In the lab we saw this relationship because the moles of solute (the blue dye) would decrease as we increased the amount of water in the solution and the solution became much more diluted. The next important concept that was learned from the lecture quiz is that volume is temperature dependent. This has to do with molarity and when temperature does go up the volume also goes up and the molarity will then decrease. We also learned about the different kind of pippetes, their usages, and how they affect how many moles of a solution and the volume of the solution depending on what kind of pipette you’re using.

            After looking at the lecture quiz, we worked with some stoich problems. We used the knowledge that we previously had on moles, molar mass, and the relationship between grams and moles. With this knowledge we were able to solve a lot of problems involving these concepts. The equation that we used a lot was moles x molar mass=weight. By using this equation, we were able to see the relationship between moles, mass, weight, and atoms in the many problems we did.

            The last thing we did this week was a lab looking at the relationship between concentration and absorbency. We performed this lab by first altering the concentration of many different solutions of blue #1 dye and water and finding the absorbency of these varying solutions. Then we looked at the different absorbency levels of blue #1 dye in Powerade and G2 to find the concentration of blue #1 dye in these solutions. We developed a linear equation between these two variables and were able to perform calculations with this knowledge. This lab connected everything we learned from the lecture quiz and stoich problems.

            We came to know and understand these concepts through experimentation and doing problems in class. I am still a little bit confused on Beer’s Law and there was a problem in the lab that required us to use this law. I would just like to grasp a better understanding of this relationship. I thought I did a good job in participating in the activities we did this week and this gave me a really good understanding of what we are doing. On a scale of 1-5, I would say I am at about a 4 on this material and I don’t really have any new questions to ask about the material.