9/9/13-9/13/13

This week in AP chemistry, I learned more about the mole and was introduced to the concept of molarity. A mole of anything equals 6.022 x 10^23 of that thing (For example, a mole of atoms is 6.022 x 10^23 atoms, a mole of molecules is 6.022 x 10^23 molecules, etc. There could even be a mole of moles, 6.022 x 10^23 moles). The mole is not a measure of mass, but is rather a quantity. The mole's mass depends on the mass of the substance. The mass of a mole of a substance equals the atomic mass of the substance, but in grams instead of atomic mass units. For example, an atom of Hydrogen has a mass of 1.01 amu while a mole of Hydrogen has a mass of 1.01 g. To help learn the concept I had to complete a lecture quiz on the mole as well as the Stoichiometry 1 & 2 worksheet. Additionally, we worked on an in class worksheet that included calculations involving the mole.

The Stoichiometry 1 & 2 tied into another concept that I learned this week, dimensional analysis. Dimensional analysis is a method of calculating that involves units. By using dimensional analysis, you can make sure that you are doing the correct kind of calculations and ensure that you are ending with the correct unit. In addition to the Stoichiometry 1 & 2 worksheet, I also had to complete a lecture quiz on dimensional analysis.

In addition to the mole, I learned about molarity. As one can tell from the name, molarity is related to the mole. Molarity (M) equals the moles of the solute divided by the volume of the solution in liters. It is one way to measure the concentration of a solution. Molarity was a central part of a lab that I completed over the course of the latter half of the week. In the lab, I measured absorbance of solutions composed of stock solution (water with blue #1 dye) and water, as well as the absorbance of blue Gatorade. I accomplished this with a partner using a device called a Spectrophotometer. As a class, we calculated the concentration of the solutions using the equation M1 x V1 = M2 x V2. I was initially unclear as to how the concentration was calculated. However, as I finished up the lab this weekend I figured out how this was accomplished. Additionally, I was not entirely sure I did some of the post-lab questions correctly. I struggled with the question that asked you to determine the molar concentration of the blue #1 in the sports drink. I know that we covered how to do that using Beer's law in class, but I still do not fully understand Beer's law. From the notes I took in class I was able to calculate the concentration of these substances, but I am unsure if my calculations are correct. This also made me unsure of the subsequent question (which read: "Determine the mass of the blue dye #1 found in 500 mL of the drink.") I understood how to calculate this because we went over it in class of Friday, however because I was unsure of my calculations in the previous question I was unsure my solution for this question was correct. The numbers I got seemed to be larger than the ones that we calculated in class. I also feel I did a insufficient job on the lab. I think my procedure was not in depth enough and in general I did a sloppy job in formatting the entire lab. That is certainly something I need to improve on next time.

Of the concepts that we covered this week I feel as though I have a sufficient understanding of the mole and dimensional analysis. I don't have an as strong understanding of Molarity and I think that I need to go over that more. With that being said, this week I got a better understanding of the mole and I have learned to think of it more as a quantity rather than a unit with mass.