Percentage+Composition

=Percentage Composition [textbook p90] = = = = = =Key Concepts=

Definition: " Percentage Composition of a compound is a relative measure of the mass of each different element present in the compound ." ([]) Definition from our notes: A list of elements present in a compound and the mass percent of each. "When two or more types of things (ingredients) are mixed together, it is common to speak of the individual ingredients as making up a certain percentage of the whole" ([]) (IF YOU WANT TO KNOW MORE INFORMATION).

How to do percentage composition questions: Steps: 1). Determine the molar mass of the compound. 2). Determine the molar mass of each of the elments within the compound.(TOTAL MASS of each element present in the formula of the compound.) 3). Set up the equation below for each particular element:

= = = __Element molar mass× # of atoms of the particular element ×100%__ = = Compound molar mass =

I.E What's the percentage composition of CH 4 ? total mass of C in compound=12.0g total mass of H in compound=1.0g× 4=4.0g % of C in compound= 12.0g/16.0g×100%=75.0% % of H in compound=4.0g/16.0g×100%=25.0%

When you are asked to determine the percentage composition of a compound, it should be understood that this refers to the percentage by mass. In other words, the percentage composition of water shows what percentage of the mass of a water molecule is made up of hydrogen and what percentage of the mass is made up of oxygen. " ([])

When doing mass percent calculations, it is always a good idea to check to make sure your mass percents add up to 100% (helps catch math errors): 75.0%+25.0%=100%

Note: There's a practice game in this page below, you can set the # of each element in the textbox and click caculate and see what happens. Enjoy you time. []

[] You can also use thess webpages to study for this concept. []

There are 2 videos showe in these webpages, in case you don't get this idea or you want to know more. You can always click here. []= []