Part 1: Percent Composition

Our Friend! The Periodic Table!

Over the past few weeks we have been focusing on some pretty big ideas. Above is a scanned image of the notes I took over three big concepts that we have been working on:
1. Percent Composition
2. Empirical Formulas
3. Molecular Formulas

First we worked on Percent Composition which is probably my favorite thing we have been doing. It takes some help from our friend the periodic table. Above on the left side of the scanned image of my notes you can see the formulas C5H8NO4. And you can see the rows of numbers below each letter. What does this mean? Well to find percent composition, we first need to look at the periodic table. C is the symbol for Carbon and when we look we see that the atomic mass is 12.011. In our formula there 5 Carbons. Sooooo...12x5 is 60. Then we do the same thing for the other symbols...Hydrogen has an atomic mass of 1.0079 (Hint: I round the numbers when I add them) so, 1x8 is 8. Then we move on to Nitrogen and Oxygen. At the end of it all, as you can see above, after we add together all our numbers we end up with 146. This is an important number because we need it to find the percent compositions of each Element in this formula. In the scanned image above I found the percent composition of Carbon in this formula. How did I do this? I divided the total mass of Carbon in this formula by the total mass of all of the elements. Which looks something like this: 60/146. Which is... .4109 and so on. Moving the decimal over we find that our percent composition of Carbon in this formula is 41.1%! This can be applied to any of the elements in the formula. For example the percent composition of Oxygen in the formula is 64/146 which comes out to .4383...43.8%!

Percent Composition is probably the most simple thing (to me anyway) that we have been working on. And I have really enjoyed working with problems to find Percent Composition!