Mole Classwork

Here is just a lovely picture of some of the work I've been doing in class. I've been working in our Glenco Chemistry book.  Page 221, Chapter Eleven, Problems 42-57 to be exact and if it helps. These have all been over subjects the include: empirical formula, moles, and molecular formula. For example, problem 50 asks:

"What is the empirical formula for a compound that contains 10.89% magnesium, 31.77% chlorine, and 57.34% oxygen?"


To solve this problem I first wrote down everything I knew which looked a lot like this:

Magnesium: 10.89%

Chlorine: 31.77%

Oxygen: 57.43%

Then I found the relative atomic mass in grams of each element (24.3 for Mg, 35.5 for Cl, and 16 for O). I then took the percent of the element and divided it by its weight, getting numbers such as: .448, .895, and 3.584 respectively. 

Now for an empirical formula, you have to find the smallest working ratios between all the elements. Because Mg came up with the smallest number, .448, it will serve as 1 in the ratio. Then take the remaining numbers, .895 and 3.584, and divide them by .448. You will then get about 2 and 8 respectively. This completes your ratio, which is 1:2:8. This means that more every one Magnesium there are two chlorines, and eight oxygens. The complete empirical formula woud then be MCl2O8.

And that's what I've been doing in class. Lots of math.