Percent Composition %

WELL! Today we learned something new. Something Fresh. Something that sounds harder than it really is!
Percent Composition is a relative measure of the mass of each different element present in the compound.

A formula that may help is : % Composition = Mass of element / mass of compound x 100

Here is an example:
1) Calculate the % composition of NaCl
    1. Find its molar mass: 22.99 + 35.45 = 58.44
    2. Calculate the amount of Na: 1 Na = 22.99
    3. Calculate the weight compared to NaCl: 22.99/58.44 = 39.34%
    4.  Calculate the total Cl present : 1 Cl = 35.45%
    5. Fine the weight compared to NaCl: 35.45/58.44 = 60.66%
* Note: Weight MUST add up to 100%, if not then there is an error in the calculations

Practice Questions:

1.Calculate the percent by weight of each element present in ammonium phosphate [(NH₄)₃PO₄]

2. Bicarbonate of soda (sodium hydrogen carbonate) is used in many commercial preparations. Its formula is NaHCO₃. Find the mass percentages (mass %) of Na, H, C, and O in sodium hydrogen carbonate. 

Well! It is pretty straight forward. This is pretty much what we learned all class!

Here is a very instructive video on how to calculate percent composition if it still confuses you!

http://www.youtube.com/watch?v=xbEeyT8nK84