This week in Chemistry we mainly white boarded worksheets in preparation for our test on Friday on Unit 5. By the end of unit 5 I found myself enjoying the concepts more. Unit 5 consisted much more of math as we did many problems that focused on finding the molecular and empirical formulas. I enjoyed this more because usually I am good at math and working with moles in chemistry has proved to come very naturally to me.
Over the weekend we worked on a worksheet where we mostly had to convert grams to moles. Because I was gone on the Friday before, this worksheet had really confused me. I couldn’t remember what labels to use when setting up the equations or even how to set them up, so it made it difficult for me. However I was relieved on Monday in class when we were given time to work out the problems with our table groups and clarify the things I wasn’t sure about. As we talked as a class and reviewed concepts of converting from moles to grams or vise versa, I learned that we must always have units on our numbers, and that the correct way to set up one of these equations is to multiply fractions rather than divide in order to put more detail in and create opportunity for extra labeling. Once I actually started doing this instead of using “naked numbers” I was fascinated to see that I was doing better with the problems and it certainly made it easier to study when I reviewed for the test.
Continuing our Unit 5 review we did a worksheet in class that explored more of finding the empirical and molecular formulas. Because we had cleared many things up the day before, I was ready to take on this higher level of chemistry. I understood the difference between empirical and molecular formulas right away, whereas I noticed other students were having trouble grasping it. Empirical formulas are based on experimental evidence and are the lowest whole number ratio for the elements in a compound, where molecular formulas are formulas containing the actual number of atoms in a compound, as shown in the following particle diagram below.
Sometimes the empirical formulas are the molecular formulas, but not always, which is why we have to be careful. The only way to determine which formula it is is by finding the compound’s grams per mole and seeing if it is consistent with the molar mass of the empirical formula. This makes me wonder if we are going to be doing a lab soon where we will have to find these formulas and determine what the formula is. However I am confused by how we would find the molar mass for the compound we would be working with unless it is given to us. And even though I understand this concept fairly well, I still feel I need more practice determining which one to use because it is not always clear.
At the end of the week we had our Unit 5 test which I feel went very well for me, thanks to our collaboration in class over the week, and I feel I am doing a good job of understanding the concepts. I still need to work on memorizing more of the atomic numbers, because it would make the work much quicker, and more practice using significant figures. Overall I enjoyed seeing how math is so vital in chemistry and I’m curious to see how we will apply these skills to real life situations such as in a lab.
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